Creatininase from Pseudomonas sp. is a homohexameric enzyme with a molecular mass of 28.4 kDa per subunit. It is a cyclic amidohydrolase catalysing the reversible conversion of creatinine to creatine. Each monomer contains a binuclear zinc centre near the C termini of the β-strands and the N termini of the main α-helices. These zinc ions indicate the location of the active site.