Shy is a proteobacterial steroid hydratase which catalyzes steroid side chain degradation without requiring a catalytically inert partner domain.

Shy (side chain hydratase) and Sal (side chain aldolase), are involved in successive reactions in the pathway of bile acid side chain catabolism in Proteobacteria. Untagged Shy copurified with His-tagged Sal indicating that the two enzymes form a complex. Shy contains a MaoC and a DUF35 domain.

Bacterial Hydratases Involved in Steroid Side Chain Degradation Have Distinct Substrate Specificities.

Actinobacterial MaoC family enoyl coenzyme A (CoA) hydratases catalyze the addition of water across the double bond of CoA esters during steroid side chain catabolism. We determined that heteromeric MaoC type hydratases, exemplified by ChsH1-ChsH2 of Mycobacterium tuberculosis and CasM-CasO from Rhodococcus jostii RHA1, are specific toward a 3-carbon side chain steroid metabolite, consistent with their roles in the last β-oxidation cycle of steroid side chain degradation. Hydratases containing two fused MaoC domains are responsible for the degradation of longer steroid side chains.