Structural and biochemical mechanism of short-chain enoyl-CoA hydratase (ECHS1) substrate recognition

Deficiency of short-chain enoyl-CoA hydratase (ECHS1), a crucial enzyme in fatty acid metabolism through the mitochondrial β-oxidation pathway, has been strongly linked to various diseases, especially cardiomyopathy. However, the structural and biochemical mechanisms through which ECHS1 recognizes acyl-CoAs remain poorly understood. Herein, cryo-EM analysis reveals the apo structure of ECHS1 and structures of the ECHS1-crotonyl-CoA, ECHS1-acetoacetyl-CoA, ECHS1-hexanoyl-CoA, and ECHS1-octanoyl-CoA complexes at high resolutions. The mechanism through which ECHS1 recognizes its substrates varies with the fatty acid chain lengths of acyl-CoAs. Furthermore, crucial point mutations in ECHS1 have a great impact on substrate recognition, resulting in significant changes in binding affinity and enzyme activity, as do disease-related point mutations in ECHS1. The functional mechanism of ECHS1 is systematically elucidated from structural and biochemical perspectives. These findings provide a theoretical basis for subsequent work focused on determining the role of ECHS1 deficiency (ECHS1D) in the occurrence of diseases such as cardiomyopathy.