CMBL is a 245 amino acid cytosolic protein and cysteine hydrolase that preferentially cleaves cyclic esters. A member of the dienelactone hydrolase family, CMBL is the human homolog of Pseudomonas dienelactone hydrolase, a protein that participates in the bacterial halocatechol degradation pathway. CMBL is ubiquitously expressed with high expression in liver, colon, kidney and small intestine, where it acts as a bioactivating enzyme for a prodrug type angiotensin II type 1 receptor antagonist known as olmesartan medoxomil. CMBL is inhibited by p-chloromercuribenzoate (PCMB) and is encoded by a gene that maps to human chromosome 5p15.2. Chromosome 5 contains 181 million base pairs and comprises nearly 6% of the human genome. Deletion of the p arm of chromosome 5 leads to Cri du chat syndrome, while deletion of the q arm, or of chromosome 5 altogether, is common in therapy-related acute myelogenous leukemias and myelodysplastic syndrome.