Amontillado (AMON, dPC2) is the Drosophila ortholog of neuroendocrine prohormone convertase 2, a soluble subtilisin/kexin-family (peptidase S8) serine endopeptidase of the regulated secretory pathway. It is made as a signal-peptide- and prodomain-containing zymogen, and its maturation and secretion as an active enzyme require the neuroendocrine helper protein 7B2 and an insect-cell processing context. In peptidergic neurons of the brain and ventral nerve cord, in corpora cardiaca endocrine cells and in midgut enteroendocrine cells it cleaves neuropeptide and peptide-hormone precursors at basic sites; it is required for production of mature adipokinetic hormone (and hence normal circulating sugar levels) and of many other neurohemal and enteroendocrine peptides. Loss of amon impairs peptide-dependent hatching, larval molting, wandering and pupal development.
| GO Term | Evidence | Action | Reason |
|---|---|---|---|
| GO:0002165 instar larval or pupal development | IMP PMID:19559693 The proprotein convertase amontillado (amon) is required dur... | KEEP AS NON CORE | Summary: Pupal and larval developmental progression depends on amon. Reason: Conditional rescue shows stage-specific requirements during larval molting and pupal development; these are downstream consequences of peptide-hormone processing rather than a direct activity of amon. Supporting Evidence: PMID:19559693 amon is required during pupal development for head eversion, leg and wing disc extension, and abdominal differentiation. |
| GO:0004252 serine-type endopeptidase activity | EXP PMID:10749852 Interaction of Drosophila melanogaster prohormone convertase... | ACCEPT | Summary: Amontillado is a catalytically active prohormone-processing serine endopeptidase. Reason: Direct fly evidence: active dPC2 appears in S2-cell medium with 7B2, a catalytic-histidine mutant fails to rescue hatching, and mature AKH is lost in mutants. The IBA comes from PTN002451026, the subtilisin/kexin node seeded by many experimentally characterised convertases including human PCSK2 (P16519) in the same PTHR42884:SF13 subfamily and amon itself; amon retains the Asp/His/Ser catalytic triad, so it lies inside the clade that inherited the activity. The IEA (EC 3.4.21.94/InterPro) agrees. Supporting Evidence: PMID:10749852 when dPC2 and either d7B2 or r7B2 were coexpressed in Drosophila S2 cells, abundant immunoreactive dPC2 was secreted into the medium, coincident with the appearance of PC2 activity. PMID:10436051 Ubiquitous expression of amontillado can restore near wild-type levels of this behavior, whereas expression of amontillado with an alanine substitution for the catalytic histidine cannot. PMID:20523747 mass spectrometric profiling shows that the production of mature AKH is inhibited in amon mutants. |
| GO:0004252 serine-type endopeptidase activity | IBA GO_REF:0000033 | ACCEPT | Summary: Amontillado is a catalytically active prohormone-processing serine endopeptidase. Reason: Direct fly evidence: active dPC2 appears in S2-cell medium with 7B2, a catalytic-histidine mutant fails to rescue hatching, and mature AKH is lost in mutants. The IBA comes from PTN002451026, the subtilisin/kexin node seeded by many experimentally characterised convertases including human PCSK2 (P16519) in the same PTHR42884:SF13 subfamily and amon itself; amon retains the Asp/His/Ser catalytic triad, so it lies inside the clade that inherited the activity. The IEA (EC 3.4.21.94/InterPro) agrees. Supporting Evidence: PMID:10749852 when dPC2 and either d7B2 or r7B2 were coexpressed in Drosophila S2 cells, abundant immunoreactive dPC2 was secreted into the medium, coincident with the appearance of PC2 activity. PMID:10436051 Ubiquitous expression of amontillado can restore near wild-type levels of this behavior, whereas expression of amontillado with an alanine substitution for the catalytic histidine cannot. PMID:20523747 mass spectrometric profiling shows that the production of mature AKH is inhibited in amon mutants. |
| GO:0004252 serine-type endopeptidase activity | IEA GO_REF:0000120 | ACCEPT | Summary: Amontillado is a catalytically active prohormone-processing serine endopeptidase. Reason: Direct fly evidence: active dPC2 appears in S2-cell medium with 7B2, a catalytic-histidine mutant fails to rescue hatching, and mature AKH is lost in mutants. The IBA comes from PTN002451026, the subtilisin/kexin node seeded by many experimentally characterised convertases including human PCSK2 (P16519) in the same PTHR42884:SF13 subfamily and amon itself; amon retains the Asp/His/Ser catalytic triad, so it lies inside the clade that inherited the activity. The IEA (EC 3.4.21.94/InterPro) agrees. Supporting Evidence: PMID:10749852 when dPC2 and either d7B2 or r7B2 were coexpressed in Drosophila S2 cells, abundant immunoreactive dPC2 was secreted into the medium, coincident with the appearance of PC2 activity. PMID:10436051 Ubiquitous expression of amontillado can restore near wild-type levels of this behavior, whereas expression of amontillado with an alanine substitution for the catalytic histidine cannot. PMID:20523747 mass spectrometric profiling shows that the production of mature AKH is inhibited in amon mutants. |
| GO:0005576 extracellular region | IBA GO_REF:0000033 | ACCEPT | Summary: The processed enzyme can be secreted. Reason: Active dPC2 is detected in conditioned medium of S2 cells coexpressing 7B2 (IDA). The IBA from PC2 node PTN000082858 (amon, mouse Pcsk2, human PCSK2) and the UniProt SubCell 'Secreted' IEA agree. The absence of secretion from HEK cells reflects insect-specific maturation requirements, not a contradiction. Supporting Evidence: PMID:10749852 when dPC2 and either d7B2 or r7B2 were coexpressed in Drosophila S2 cells, abundant immunoreactive dPC2 was secreted into the medium, coincident with the appearance of PC2 activity. |
| GO:0005576 extracellular region | IDA PMID:10749852 Interaction of Drosophila melanogaster prohormone convertase... | ACCEPT | Summary: The processed enzyme can be secreted. Reason: Active dPC2 is detected in conditioned medium of S2 cells coexpressing 7B2 (IDA). The IBA from PC2 node PTN000082858 (amon, mouse Pcsk2, human PCSK2) and the UniProt SubCell 'Secreted' IEA agree. The absence of secretion from HEK cells reflects insect-specific maturation requirements, not a contradiction. Supporting Evidence: PMID:10749852 when dPC2 and either d7B2 or r7B2 were coexpressed in Drosophila S2 cells, abundant immunoreactive dPC2 was secreted into the medium, coincident with the appearance of PC2 activity. |
| GO:0005576 extracellular region | IEA GO_REF:0000044 | ACCEPT | Summary: The processed enzyme can be secreted. Reason: Active dPC2 is detected in conditioned medium of S2 cells coexpressing 7B2 (IDA). The IBA from PC2 node PTN000082858 (amon, mouse Pcsk2, human PCSK2) and the UniProt SubCell 'Secreted' IEA agree. The absence of secretion from HEK cells reflects insect-specific maturation requirements, not a contradiction. Supporting Evidence: PMID:10749852 when dPC2 and either d7B2 or r7B2 were coexpressed in Drosophila S2 cells, abundant immunoreactive dPC2 was secreted into the medium, coincident with the appearance of PC2 activity. |
| GO:0006508 proteolysis | IDA PMID:10749852 Interaction of Drosophila melanogaster prohormone convertase... | MODIFY | Summary: Proteolysis is correct but peptide hormone processing is the specific supported process. Reason: Amon-dependent proteolysis is precursor processing of neuropeptide/peptide-hormone precursors. GO:0016486 peptide hormone processing is an is_a descendant of proteolysis (via protein processing) and is already annotated to amon by IMP and IBA, so the generic term is refined to it. Proposed replacements: peptide hormone processing Supporting Evidence: PMID:10749852 when dPC2 and either d7B2 or r7B2 were coexpressed in Drosophila S2 cells, abundant immunoreactive dPC2 was secreted into the medium, coincident with the appearance of PC2 activity. PMID:20523747 mass spectrometric profiling shows that the production of mature AKH is inhibited in amon mutants. |
| GO:0006508 proteolysis | IEA GO_REF:0000002 | MODIFY | Summary: Proteolysis is correct but peptide hormone processing is the specific supported process. Reason: Amon-dependent proteolysis is precursor processing of neuropeptide/peptide-hormone precursors. GO:0016486 peptide hormone processing is an is_a descendant of proteolysis (via protein processing) and is already annotated to amon by IMP and IBA, so the generic term is refined to it. Proposed replacements: peptide hormone processing Supporting Evidence: PMID:10749852 when dPC2 and either d7B2 or r7B2 were coexpressed in Drosophila S2 cells, abundant immunoreactive dPC2 was secreted into the medium, coincident with the appearance of PC2 activity. PMID:20523747 mass spectrometric profiling shows that the production of mature AKH is inhibited in amon mutants. |
| GO:0008233 peptidase activity | IDA PMID:10749852 Interaction of Drosophila melanogaster prohormone convertase... | MODIFY | Summary: Serine endopeptidase activity specifies generic peptidase activity. Reason: Correct but generic: the IDA activity is a dibasic-site prohormone convertase activity of a subtilisin-family serine protease. GO:0004252 serine-type endopeptidase activity is a descendant of peptidase activity and is already on the gene (EXP/IBA). Proposed replacements: serine-type endopeptidase activity Supporting Evidence: PMID:10749852 when dPC2 and either d7B2 or r7B2 were coexpressed in Drosophila S2 cells, abundant immunoreactive dPC2 was secreted into the medium, coincident with the appearance of PC2 activity. |
| GO:0008236 serine-type peptidase activity | IEA GO_REF:0000002 | MODIFY | Summary: The relevant serine peptidase reaction is endoproteolysis. Reason: Correct but generic InterPro mapping. PC2 cleaves within prohormone chains (endoproteolysis), so GO:0004252, an is_a descendant already carried by the gene, is the supported specific term. Proposed replacements: serine-type endopeptidase activity Supporting Evidence: PMID:10749852 when dPC2 and either d7B2 or r7B2 were coexpressed in Drosophila S2 cells, abundant immunoreactive dPC2 was secreted into the medium, coincident with the appearance of PC2 activity. |
| GO:0016020 membrane | IBA GO_REF:0000033 | UNDECIDED | Summary: Generic membrane association is inherited from a deep convertase node and is not established for amon. Reason: This IBA is placed at PTN002451026, a deep subtilisin/kexin node whose donors are dominated by membrane-anchored convertases (furin, KEX2, PCSK7) but also include human PCSK2. Amon has a signal peptide and no transmembrane segment, and the only fly localisation data show secretion. Peripheral association of PC2 with secretory-granule membranes is reported for mammals but not tested in fly, so neither acceptance nor removal is warranted on current evidence. Propagation Review Root cause: UNRESOLVED Failure modes: COMPARTMENT OR COMPLEX MISMATCH Sources checked: PANTHER:PTN002451026 Β· subtilisin/kexin convertase node SUPPORTS SOURCE BUT NOT TARGET Deep node spanning membrane-anchored furin, KEX2 and PCSK7 as well as soluble PC1/PC2; generic membrane fits the anchored members directly but is only peripheral, if at all, for the soluble PC2 lineage. UniProtKB:P16519 Β· PCSK2 UNRESOLVED Human PC2, in the same PTHR42884:SF13 subfamily, is among the donors, so membrane association is grounded for at least one PC2; no fly test exists. Supporting Evidence: PMID:10749852 when dPC2 and either d7B2 or r7B2 were coexpressed in Drosophila S2 cells, abundant immunoreactive dPC2 was secreted into the medium, coincident with the appearance of PC2 activity. file:DROME/amon/amon-deep-research-falcon.md Because AMON lacks a transmembrane domain, it is not a cell-surface receptor or membrane-tethered convertase. |
| GO:0016486 peptide hormone processing | IBA GO_REF:0000033 | ACCEPT | Summary: Peptide hormone processing is the central biological function, shown directly in fly. Reason: Mass spectrometry shows loss of mature AKH, ring-gland and perisympathetic-organ neuropeptides, and reduced enteroendocrine peptides in amon mutants, and amon itself supplies the cleavage step (it is the enzyme, not the substrate). The IBA from the bilaterian PC2 node PTN000082858 (seeded by amon, human/mouse/rat PC2 and C. elegans egl-3) agrees. Supporting Evidence: PMID:20523747 mass spectrometric profiling shows that the production of mature AKH is inhibited in amon mutants. PMID:21138435 A loss of amon correlates with a loss of neuropeptide hormone signals from the larval ring gland and perisympathetic organs. PMID:21214272 All enteroendocrine peptides represent brain-gut peptides, and apparently are processed by Drosophila prohormone convertase 2 (AMON) as suggested by impaired peptide detectability in amon mutants |
| GO:0016486 peptide hormone processing | IEA GO_REF:0000117 | ACCEPT | Summary: Peptide hormone processing is the central biological function, shown directly in fly. Reason: Mass spectrometry shows loss of mature AKH, ring-gland and perisympathetic-organ neuropeptides, and reduced enteroendocrine peptides in amon mutants, and amon itself supplies the cleavage step (it is the enzyme, not the substrate). The IBA from the bilaterian PC2 node PTN000082858 (seeded by amon, human/mouse/rat PC2 and C. elegans egl-3) agrees. Supporting Evidence: PMID:20523747 mass spectrometric profiling shows that the production of mature AKH is inhibited in amon mutants. PMID:21138435 A loss of amon correlates with a loss of neuropeptide hormone signals from the larval ring gland and perisympathetic organs. PMID:21214272 All enteroendocrine peptides represent brain-gut peptides, and apparently are processed by Drosophila prohormone convertase 2 (AMON) as suggested by impaired peptide detectability in amon mutants |
| GO:0016486 peptide hormone processing | IMP PMID:20523747 The proprotein convertase encoded by amontillado (amon) is r... | ACCEPT | Summary: Peptide hormone processing is the central biological function, shown directly in fly. Reason: Mass spectrometry shows loss of mature AKH, ring-gland and perisympathetic-organ neuropeptides, and reduced enteroendocrine peptides in amon mutants, and amon itself supplies the cleavage step (it is the enzyme, not the substrate). The IBA from the bilaterian PC2 node PTN000082858 (seeded by amon, human/mouse/rat PC2 and C. elegans egl-3) agrees. Supporting Evidence: PMID:20523747 mass spectrometric profiling shows that the production of mature AKH is inhibited in amon mutants. PMID:21138435 A loss of amon correlates with a loss of neuropeptide hormone signals from the larval ring gland and perisympathetic organs. PMID:21214272 All enteroendocrine peptides represent brain-gut peptides, and apparently are processed by Drosophila prohormone convertase 2 (AMON) as suggested by impaired peptide detectability in amon mutants |
| GO:0016486 peptide hormone processing | IMP PMID:21138435 Deficiency of prohormone convertase dPC2 (AMONTILLADO) resul... | ACCEPT | Summary: Peptide hormone processing is the central biological function, shown directly in fly. Reason: Mass spectrometry shows loss of mature AKH, ring-gland and perisympathetic-organ neuropeptides, and reduced enteroendocrine peptides in amon mutants, and amon itself supplies the cleavage step (it is the enzyme, not the substrate). The IBA from the bilaterian PC2 node PTN000082858 (seeded by amon, human/mouse/rat PC2 and C. elegans egl-3) agrees. Supporting Evidence: PMID:20523747 mass spectrometric profiling shows that the production of mature AKH is inhibited in amon mutants. PMID:21138435 A loss of amon correlates with a loss of neuropeptide hormone signals from the larval ring gland and perisympathetic organs. PMID:21214272 All enteroendocrine peptides represent brain-gut peptides, and apparently are processed by Drosophila prohormone convertase 2 (AMON) as suggested by impaired peptide detectability in amon mutants |
| GO:0016486 peptide hormone processing | IMP PMID:21214272 Peptidomics and peptide hormone processing in the Drosophila... | ACCEPT | Summary: Peptide hormone processing is the central biological function, shown directly in fly. Reason: Mass spectrometry shows loss of mature AKH, ring-gland and perisympathetic-organ neuropeptides, and reduced enteroendocrine peptides in amon mutants, and amon itself supplies the cleavage step (it is the enzyme, not the substrate). The IBA from the bilaterian PC2 node PTN000082858 (seeded by amon, human/mouse/rat PC2 and C. elegans egl-3) agrees. Supporting Evidence: PMID:20523747 mass spectrometric profiling shows that the production of mature AKH is inhibited in amon mutants. PMID:21138435 A loss of amon correlates with a loss of neuropeptide hormone signals from the larval ring gland and perisympathetic organs. PMID:21214272 All enteroendocrine peptides represent brain-gut peptides, and apparently are processed by Drosophila prohormone convertase 2 (AMON) as suggested by impaired peptide detectability in amon mutants |
| GO:0017171 serine hydrolase activity | HDA PMID:33827210 A Superfamily-wide Activity Atlas of Serine Hydrolases in &l... | MODIFY | Summary: Serine hydrolase activity is true but generic; serine-type endopeptidase is the specific supported activity. Reason: The HDA comes from an activity-based serine hydrolase probe atlas, which establishes an active nucleophilic serine but not the reaction. GO:0004252 serine-type endopeptidase activity is an is_a descendant of serine hydrolase activity and is supported for amon by direct S2-cell activity data. Proposed replacements: serine-type endopeptidase activity Supporting Evidence: PMID:33827210 we identify and globally map the full complement of SH activities during various developmental stages and in different adult tissues of Drosophila PMID:10749852 when dPC2 and either d7B2 or r7B2 were coexpressed in Drosophila S2 cells, abundant immunoreactive dPC2 was secreted into the medium, coincident with the appearance of PC2 activity. |
| GO:0030537 larval behavior | IEA GO_REF:0000117 | MODIFY | Summary: Larval behavior is correct but generic; the documented defect is in larval wandering. Reason: ARBA IEA. The experimentally documented behavioural phenotype is failure of L3 larvae to enter the wandering phase; GO:0035180 larval wandering behavior is an is_a descendant already annotated by IMP. Like that row, it is a downstream peptide-hormone-dependent phenotype and non-core. Proposed replacements: larval wandering behavior Supporting Evidence: PMID:21138435 The lack of AMON activity resulted in a deficiency of L3 larva to enter the wandering phase. |
| GO:0033500 carbohydrate homeostasis | IMP PMID:20523747 The proprotein convertase encoded by amontillado (amon) is r... | KEEP AS NON CORE | Summary: Sugar homeostasis depends on AKH precursor processing. Reason: Cell-specific knockdown in AKH cells lowers circulating sugars and AKH maturation fails in mutants; amon's role is the upstream AKH processing step, so this physiological outcome is non-core. Supporting Evidence: PMID:20523747 mass spectrometric profiling shows that the production of mature AKH is inhibited in amon mutants. |
| GO:0035180 larval wandering behavior | IMP PMID:21138435 Deficiency of prohormone convertase dPC2 (AMONTILLADO) resul... | KEEP AS NON CORE | Summary: Larval wandering requires amon-dependent neuropeptide production. Reason: Direct peptide-profiling study reports failure of amon-deficient L3 larvae to enter wandering; a downstream consequence of neuropeptide loss, non-core. Supporting Evidence: PMID:21138435 The lack of AMON activity resulted in a deficiency of L3 larva to enter the wandering phase. |
| GO:0035187 hatching behavior | IMP PMID:10436051 A role for amontillado, the Drosophila homolog of the neurop... | KEEP AS NON CORE | Summary: Hatching behavior requires active amontillado. Reason: Catalytic-histidine mutant fails to rescue, linking the behaviour to proteolytic peptide maturation; the behaviour itself is a downstream organismal consequence of neuropeptide production and is non-core. Supporting Evidence: PMID:10436051 Ubiquitous expression of amontillado can restore near wild-type levels of this behavior, whereas expression of amontillado with an alanine substitution for the catalytic histidine cannot. |
| GO:0043005 neuron projection | IBA GO_REF:0000033 | KEEP AS NON CORE | Summary: Neuron projection is a plausible inherited location for a neurosecretory convertase. Reason: IBA from the PC2 orthogroup node PTN000082858 (rat Pcsk2, worm egl-3). In fly, amon is expressed in peptidergic neurons whose axons innervate the ring gland, consistent with this location, but amon protein has not been specifically imaged in projections. Retained as a non-core location. Supporting Evidence: PMID:19559693 The amon protein is expressed in neuronal cells that innervate the corpus allatum and corpora cardiaca of the ring gland |
| GO:0045464 R8 cell fate specification | IMP PMID:28853393 Parallel Activin and BMP signaling coordinates R7/R8 photore... | MARK AS OVER ANNOTATED | Summary: R8 subtype specification is an indirect, RNAi-only consequence of presumed ligand processing in neighbouring R7 cells. Reason: Amon RNAi reduces pale ommatidia, and an amon reporter is enriched in pale R7. The authors propose that amon processes BMP/Activin ligands in R7, which then signal to R8; ligand cleavage by amon was not shown. Amon therefore at most supplies a ligand-maturation step in a different cell, so 'involved in R8 cell fate specification' overstates its participation. The curator's IMP is kept visible but flagged as over-annotation. Supporting Evidence: PMID:28853393 We propose a model where pale R7-specific ligand processing by Amon and possibly additional factors instructs non-redundant signaling by two arms of the TGFΞ² family to specify pale R8 subtypes |
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Download this section (compressed HTML)Q: Is Drosophila 7B2 required in vivo for amon activation, and do 7B2 mutants phenocopy amon loss of peptide maturation?
Q: Does amon directly cleave BMP/Activin ligand precursors in pale R7 cells, or is the R8 subtype phenotype mediated by a neuropeptide?
Experiment: Express amon with d7B2 in S2 cells and assay cleavage of recombinant AKH precursor and Dpp/Actbeta precursors, with catalytic-triad mutants as negative controls, mapping cleavage sites by mass spectrometry.
Hypothesis: Amon directly cleaves the AKH precursor and selected TGF-beta ligand precursors at basic sites.
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Download this section (compressed HTML)amontillado (amon) encodes a member of the Prohormone Convertase (PC) family of proteolytic enzymes. PCs generally recognize conserved basic amino acid sequences within protein precursors to direct catalysis of specific cleavage. amon product directly cleaves sli protein and may also target the propeptide encoded by Akh. It is also required for the production of bioactive neuropeptide hormones (e.g. those encoded by Hug, Crz, Ms, Capa and sNPF).
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