Ckmt2

UniProt ID: P09605
Organism: Rattus norvegicus
Review Status: COMPLETE
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Gene Description

Ckmt2 encodes rat mitochondrial creatine kinase S-type, a mitochondrial phosphotransferase that reversibly transfers phosphate between ATP and creatine to support phosphocreatine-based energy buffering in tissues with high energy demand. The review accepts creatine kinase activity and phosphocreatine biosynthesis as core and marks broad kinase/transferase and developmental expression annotations as non-core or over-annotated.

Existing Annotations Review

GO Term Evidence Action Reason
GO:0004111 creatine kinase activity
IBA
GO_REF:0000033
ACCEPT
Summary: Ckmt2 is a mitochondrial creatine kinase S-type; the creatine kinase activity annotation is supported by the fetched UniProt/GOA evidence (IBA, GO_REF:0000033) and represents a core or direct activity/process.
Reason: This term captures a directly supported part of Ckmt2 core biochemistry or the closest GO process for that activity.
Supporting Evidence:
UniProtKB:P09605
GO; GO:0004111; F:creatine kinase activity; IBA:GO_Central.
file:rat/Ckmt2/Ckmt2-deep-research-falcon.md
CKMT2 is a **phosphotransferase** transferring the Ξ³-phosphoryl group of ATP to creatine.
GO:0005739 mitochondrion
IBA
GO_REF:0000033
KEEP AS NON CORE
Summary: The mitochondrion annotation is plausible for Ckmt2 but should be kept as non-core context rather than used to define the gene product function.
Reason: The localization is useful context but is not the core molecular function of Ckmt2.
Supporting Evidence:
UniProtKB:P09605
GO; GO:0005739; C:mitochondrion; IBA:GO_Central.
file:rat/Ckmt2/Ckmt2-deep-research-falcon.md
Mitochondrial CK is localized to the **mitochondrial intermembrane and cristae space** and assembles into **cuboidal homooctamers** that are peripherally membrane-associated.
GO:0046314 phosphocreatine biosynthetic process
IBA
GO_REF:0000033
ACCEPT
Summary: Ckmt2 is a mitochondrial creatine kinase S-type; the phosphocreatine biosynthetic process annotation is supported by the fetched UniProt/GOA evidence (IBA, GO_REF:0000033) and represents a core or direct activity/process.
Reason: This term captures a directly supported part of Ckmt2 core biochemistry or the closest GO process for that activity.
Supporting Evidence:
UniProtKB:P09605
GO; GO:0046314; P:phosphocreatine biosynthetic process; IBA:GO_Central.
file:rat/Ckmt2/Ckmt2-deep-research-falcon.md
In heart, CKMT2 is positioned to convert mitochondrial ATP into PCr, which diffuses to ATPases
GO:0003824 catalytic activity
IEA
GO_REF:0000002
MODIFY
Summary: The catalytic activity annotation is related to Ckmt2 function, but it is too generic compared with the supported specific term(s): creatine kinase activity.
Reason: The annotation is directionally related to Ckmt2 but is too broad; the specific catalytic activity is more informative.
Proposed replacements: creatine kinase activity
Supporting Evidence:
UniProtKB:P09605
FUNCTION: Reversibly catalyzes the transfer of phosphate between ATP and various phosphogens (e.g. creatine phosphate). Creatine kinase isoenzymes play a central role in energy transduction in tissues with large, fluctuating energy demands, such as skeletal muscle, heart, brain and spermatozoa.
GO:0004111 creatine kinase activity
IEA
GO_REF:0000120
ACCEPT
Summary: Ckmt2 is a mitochondrial creatine kinase S-type; the creatine kinase activity annotation is supported by the fetched UniProt/GOA evidence (IEA, GO_REF:0000120) and represents a core or direct activity/process.
Reason: This term captures a directly supported part of Ckmt2 core biochemistry or the closest GO process for that activity.
Supporting Evidence:
UniProtKB:P09605
GO; GO:0004111; F:creatine kinase activity; IBA:GO_Central.
file:rat/Ckmt2/Ckmt2-deep-research-falcon.md
CKMT2 is a **phosphotransferase** transferring the Ξ³-phosphoryl group of ATP to creatine.
GO:0005743 mitochondrial inner membrane
IEA
GO_REF:0000044
KEEP AS NON CORE
Summary: The mitochondrial inner membrane annotation is plausible for Ckmt2 but should be kept as non-core context rather than used to define the gene product function.
Reason: The localization is useful context but is not the core molecular function of Ckmt2.
Supporting Evidence:
UniProtKB:P09605
GO; GO:0005743; C:mitochondrial inner membrane; IEA:UniProtKB-SubCell.
file:rat/Ckmt2/Ckmt2-deep-research-falcon.md
Mitochondrial CK is localized to the **mitochondrial intermembrane and cristae space** and assembles into **cuboidal homooctamers** that are peripherally membrane-associated.
GO:0007519 skeletal muscle tissue development
IEA
GO_REF:0000117
MARK AS OVER ANNOTATED
Summary: The skeletal muscle tissue development annotation likely reflects indirect phenotype, expression, or pathway context rather than the direct conserved function of Ckmt2.
Reason: This term derives from the developmental mRNA expression pattern (sMtCK mRNA is markedly upregulated postnatally in skeletal muscle, PMID:8086475), which reflects the rising metabolic demand for phosphocreatine buffering as muscle matures rather than a direct instructive role of Ckmt2 in tissue development.
Supporting Evidence:
UniProtKB:P09605
GO; GO:0007519; P:skeletal muscle tissue development; IEP:RGD.
GO:0016301 kinase activity
IEA
GO_REF:0000002
MODIFY
Summary: The kinase activity annotation is related to Ckmt2 function, but it is too generic compared with the supported specific term(s): creatine kinase activity.
Reason: The annotation is directionally related to Ckmt2 but is too broad; the specific catalytic activity is more informative.
Proposed replacements: creatine kinase activity
Supporting Evidence:
UniProtKB:P09605
FUNCTION: Reversibly catalyzes the transfer of phosphate between ATP and various phosphogens (e.g. creatine phosphate). Creatine kinase isoenzymes play a central role in energy transduction in tissues with large, fluctuating energy demands, such as skeletal muscle, heart, brain and spermatozoa.
GO:0016772 transferase activity, transferring phosphorus-containing groups
IEA
GO_REF:0000002
MODIFY
Summary: The transferase activity, transferring phosphorus-containing groups annotation is related to Ckmt2 function, but it is too generic compared with the supported specific term(s): creatine kinase activity.
Reason: The annotation is directionally related to Ckmt2 but is too broad; the specific catalytic activity is more informative.
Proposed replacements: creatine kinase activity
Supporting Evidence:
UniProtKB:P09605
FUNCTION: Reversibly catalyzes the transfer of phosphate between ATP and various phosphogens (e.g. creatine phosphate). Creatine kinase isoenzymes play a central role in energy transduction in tissues with large, fluctuating energy demands, such as skeletal muscle, heart, brain and spermatozoa.
GO:0016775 phosphotransferase activity, nitrogenous group as acceptor
IEA
GO_REF:0000002
MODIFY
Summary: The phosphotransferase activity, nitrogenous group as acceptor annotation is related to Ckmt2 function, but it is too generic compared with the supported specific term(s): creatine kinase activity.
Reason: The annotation is directionally related to Ckmt2 but is too broad; the specific catalytic activity is more informative.
Proposed replacements: creatine kinase activity
Supporting Evidence:
UniProtKB:P09605
FUNCTION: Reversibly catalyzes the transfer of phosphate between ATP and various phosphogens (e.g. creatine phosphate). Creatine kinase isoenzymes play a central role in energy transduction in tissues with large, fluctuating energy demands, such as skeletal muscle, heart, brain and spermatozoa.
GO:0046314 phosphocreatine biosynthetic process
IEA
GO_REF:0000002
ACCEPT
Summary: Ckmt2 is a mitochondrial creatine kinase S-type; the phosphocreatine biosynthetic process annotation is supported by the fetched UniProt/GOA evidence (IEA, GO_REF:0000002) and represents a core or direct activity/process.
Reason: This term captures a directly supported part of Ckmt2 core biochemistry or the closest GO process for that activity.
Supporting Evidence:
UniProtKB:P09605
GO; GO:0046314; P:phosphocreatine biosynthetic process; IEA:InterPro (InterPro:IPR000749).
GO:1901612 cardiolipin binding
IDA
PMID:3972849
Cardiolipin is the membrane receptor for mitochondrial creat...
KEEP AS NON CORE
Summary: The cardiolipin binding annotation is plausible for Ckmt2 but should be kept as non-core context rather than used to define the gene product function.
Reason: This is plausible biochemical context for Ckmt2, but it is not the defining evolved activity.
Supporting Evidence:
UniProtKB:P09605
GO; GO:1901612; F:cardiolipin binding; IDA:RGD.
GO:0007507 heart development
IEP
PMID:8086475
Developmental expression of sarcomeric and ubiquitous mitoch...
MARK AS OVER ANNOTATED
Summary: The heart development annotation likely reflects indirect phenotype, expression, or pathway context rather than the direct conserved function of Ckmt2.
Reason: This IEP term derives from the developmental mRNA expression pattern reported in PMID:8086475, where sMtCK mRNA in heart is undetectable prenatally but dramatically upregulated postnatally. This pattern reflects the maturing heart's increasing metabolic demand for phosphocreatine buffering, not a direct instructive role of Ckmt2 in heart morphogenesis.
Supporting Evidence:
UniProtKB:P09605
GO; GO:0007507; P:heart development; IEP:RGD.
PMID:8086475
sMtCK mRNA in heart is undetectable prenatally but is dramatically upregulated by 28 d postnatally.
GO:0007519 skeletal muscle tissue development
IEP
PMID:8086475
Developmental expression of sarcomeric and ubiquitous mitoch...
MARK AS OVER ANNOTATED
Summary: The skeletal muscle tissue development annotation likely reflects indirect phenotype, expression, or pathway context rather than the direct conserved function of Ckmt2.
Reason: This IEP term derives from the developmental mRNA expression pattern reported in PMID:8086475, where sMtCK mRNA in skeletal muscle is extremely low prenatally but markedly upregulated at birth and doubles by 28 d postnatally. This reflects the maturing muscle's rising demand for phosphocreatine buffering, not a direct instructive role of Ckmt2 in tissue development.
Supporting Evidence:
UniProtKB:P09605
GO; GO:0007519; P:skeletal muscle tissue development; IEP:RGD.
PMID:8086475
sMtCK mRNA in skeletal muscle is also extremely low prenatally but is markedly upregulated at birth and doubles by 28 d postnatally.

Core Functions

Ckmt2 is the sarcomeric mitochondrial creatine kinase (sMtCK), distinct from the ubiquitous CKMT1 isoform. As a phosphotransferase it reversibly transfers the gamma-phosphoryl group of ATP to creatine (EC 2.7.3.2), generating phosphocreatine. Acting as a membrane-associated octamer in the mitochondrial intermembrane and cristae space, it converts mitochondrial ATP into diffusible phosphocreatine for the creatine kinase / phosphocreatine shuttle, coupling oxidative phosphorylation to cytosolic ATP demand in heart and skeletal muscle. It assembles into proteolipid contact-site complexes with cardiolipin, VDAC and ANT that support efficient high-energy phosphate transfer.

Supporting Evidence:
  • UniProtKB:P09605
    FUNCTION: Reversibly catalyzes the transfer of phosphate between ATP and various phosphogens (e.g. creatine phosphate). Creatine kinase isoenzymes play a central role in energy transduction in tissues with large, fluctuating energy demands, such as skeletal muscle, heart, brain and spermatozoa.
  • file:rat/Ckmt2/Ckmt2-deep-research-falcon.md
    CKMT2 is a **phosphotransferase** transferring the Ξ³-phosphoryl group of ATP to creatine.

References

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Deep Research

Falcon

(Ckmt2-deep-research-falcon.md)

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πŸ“š Additional Documentation

Notes

(Ckmt2-notes.md)

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