| Item | Summary statement | Key evidence citations |
|---|---|---|
| Gene/protein | **algD** in *Pseudomonas putida* KT2440 maps to **PP_1288** and is annotated as **GDP-mannose 6-dehydrogenase**; deletion analyses place PP_1277–PP_1288 as the alginate-associated cluster in this strain. | (pqac-00000000, pqac-00000005) |
| Enzyme name | AlgD is the **GDP-mannose 6-dehydrogenase (GMD)** that supplies the activated uronic-acid precursor used for alginate biosynthesis. | (pqac-00000000, pqac-00000002, pqac-00000006) |
| EC | The reviewed AlgD/GMD enzyme is identified as **EC 1.1.1.132**. | (pqac-00000008) |
| Reaction | AlgD catalyzes the **irreversible oxidation of GDP-mannose to GDP-mannuronic acid (GDP-mannuronate)**, a key precursor-forming step in bacterial alginate biosynthesis. | (pqac-00000002, pqac-00000004, pqac-00000008) |
| Cofactor | The enzyme is **NAD+-dependent**; assays monitor NADH formation during GDP-mannose oxidation, and a reviewed value for apparent **Km(NAD+) ≈ 0.36 mM** is reported for *P. aeruginosa* GMD. | (pqac-00000007, pqac-00000009) |
| Pathway/operon context | In KT2440, PP_1277–PP_1288 are presented as the **AlgD operon/alginate synthesis region**; algD is described as the **first gene in the alginate synthesis operon** and PP_1288 is functionally annotated as GDP-mannose 6-dehydrogenase. | (pqac-00000000, pqac-00000005) |
| Stress regulation evidence | Under **water limitation/matric stress**, alginate-related genes in KT2440 are transiently upregulated; the 2014 study reports **algD/PP_1288 log2-fold change = 3.26** in WT at 0.4 MPa Ψm, supporting stress-responsive activation of alginate precursor synthesis. | (pqac-00000000, pqac-00000001) |
| Structural notes | Direct KT2440 structural data were not found in this run, but reviewed AlgD/GMD homologs are described as having an **N-terminal nucleotide-binding domain** and **C-terminal catalytic domain** with an essential catalytic **Cys** residue, and crystal work supports a **domain-swapped dimer**; these features are consistent with UniProt family/domain assignment but remain **inferred for Q88NC4** rather than directly demonstrated here. | (pqac-00000004, pqac-00000007, pqac-00000012) |
| Kinetics/inhibition data | No KT2440-specific kinetic constants were found in this run. For the well-studied *P. aeruginosa* homolog, GDP-mannose shows **strong negative cooperativity** with reported **Km values of ~13 µM and ~3 mM**; substrate-analog inhibitors can be potent, including **AM5′ASG**, which gave **~90% inhibition at 0.5 mM**. These data are **supportive homolog evidence**, not KT2440-specific measurements. | (pqac-00000008, pqac-00000009, pqac-00000011) |
| Localization | The available evidence places AlgD in the **cytoplasmic precursor-synthesis stage** of alginate biosynthesis, alongside AlgA and AlgC, generating GDP-mannuronate before polymerization/export steps handled by membrane/periplasmic components. | (pqac-00000002, pqac-00000004, pqac-00000006) |


*Table: This table summarizes the evidence-supported functional annotation of algD/PP_1288 (UniProt Q88NC4) in Pseudomonas putida KT2440, including confirmed KT2440-specific findings and clearly labeled homolog-based inferences where direct strain-specific data were limited.*