Definition
Creatininase is an enzyme (EC 3.5.2.10) that catalyzes the hydrolytic deamination of creatinine to N‑methylhydantoin (also referred to as creatine). It is employed in biochemical assays for the quantitative determination of creatinine in biological fluids.
Overview
Creatininase belongs to the family of hydrolases acting on carbon‑nitrogen bonds other than peptide bonds, specifically in linear amidines. The enzymatic reaction proceeds as follows:
creatinine + H₂O → N‑methylhydantoin + NH₃
The enzyme is commonly sourced from microorganisms, particularly certain bacterial species such as Pseudomonas spp. and Alcaligenes spp., and has been isolated from fungal cultures as well. In diagnostic laboratories, creatininase is used in a multi‑enzyme system together with creatinase, sarcosine oxidase, and peroxidase to generate a measurable colorimetric or amperometric signal proportional to creatinine concentration.
Etymology / Origin
The name combines “creatinine,” the substrate on which the enzyme acts, with the suffix “‑ase,” which denotes an enzyme. The term reflects the enzyme’s specific activity toward creatinine.
Characteristics
| Property | Details |
|---|---|
| Enzyme Commission (EC) number | 3.5.2.10 |
| Systematic name | creatinine amidohydrolase |
| Alternative names | creatinine deaminase, creatinine amidase |
| Molecular mass | Typically 30–35 kDa for bacterial forms (varies with source) |
| Cofactors | No metal ion cofactors are required; activity depends on pH and temperature |
| Optimal pH | Approximately pH 7.5–8.0 |
| Optimal temperature | 30–40 °C for most microbial enzymes |
| Substrate specificity | Highly specific for creatinine; negligible activity toward structurally related compounds |
| Industrial / clinical use | Component of enzymatic creatinine assay kits for serum, plasma, and urine analysis |
Related Topics
- Creatinine – a waste product of muscle metabolism, commonly measured to assess renal function.
- Creatinase (EC 3.5.2.2) – an enzyme that hydrolyzes N‑methylhydantoin (the product of the creatininase reaction) to creatine.
- Sarcosine oxidase – used in conjunction with creatininase/creatinase in assay systems to generate hydrogen peroxide for detection.
- Enzymatic determination of creatinine – a clinical laboratory method employing a cascade of enzymes (creatinase, creatininase, sarcosine oxidase) to produce a quantifiable signal.
- Enzyme Commission (EC) classification – the systematic categorization of enzymes based on the reactions they catalyze.