Cysteine hydrolase whose endogenous substrates and physiological function are unknown. Catalyzes the hydrolytic activation of several ester-based prodrugs, by cleaving the dioxolone ring to yield their respective active metabolites, diacetyl and CO2. Can thus convert the prodrugs Olmesartan medoxomil and Azilsartan medoxomil into their active metabolites (Olmesartan and Azilsartan), two angiotensin receptor blockers. Is also able to activate beta-lactam antibiotics Faropenem medoxomil and Lenampicillin. {ECO:0000269|PubMed:20177059, ECO:0000269|PubMed:23946449}. This is the function of CMBL (carboxymethylenebutenolidase homolog, ENSG00000164237).