Journal Article

Structural insights into the reaction mechanism of S-adenosyl-L-homocysteine hydrolase

Tanaka, Nobutada, Kuroda, Daisuke, Nakamura, Kazuo T., Umeda, Tomonobu, Kitade, Yukio, Kusakabe, Yoshio, Nakanishi, Masayuki, Ishihara, Masaaki, Gouda, Hiroaki

2015

Overview

S -adenosyl- L -homocysteine hydrolase (SAH hydrolase or SAHH) is a highly conserved enzyme that catalyses the reversible hydrolysis of SAH to L -homocysteine (HCY) and adenosine (ADO). High-resolution crystal structures have been reported for bacterial and plant SAHHs, but not mammalian SAHHs. Here, we report the first high-resolution crystal structure of mammalian SAHH (mouse SAHH) in complex with a reaction product (ADO) and with two reaction intermediate analogues—3’-keto-aristeromycin (3KA) and noraristeromycin (NRN)—at resolutions of 1.55, 1.55 and 1.65 Å. Each of the three structures constitutes a structural snapshot of one of the last three steps of the five-step process of SAH hydrolysis by SAHH. In the NRN complex, a water molecule, which is an essential substrate for ADO formation, is structurally identified for the first time as the candidate donor in a Michael addition by SAHH to the 3’-keto-4’,5’-didehydroadenosine reaction intermediate. The presence of the water molecule is consistent with the reaction mechanism proposed by Palmer & Abeles in 1979. These results provide insights into the reaction mechanism of the SAHH enzyme.

• Publisher: Nature Publishing Group UK,Nature Publishing Group
• Subject: 631/45/173 / 631/45/535/1266 / 631/45/607/1164 / Adenosine / Adenosine - analogs & derivatives / Adenosine - chemistry / Adenosine - metabolism / Adenosylhomocysteinase - chemistry / Adenosylhomocysteinase - metabolism / Amino Acid Sequence / Animals / Binding Sites / Biocatalysis / Crystal structure / Crystallography, X-Ray / Enzymes / Homocysteine / Humanities and Social Sciences / Hydrolase / Hydrolysis / L-Homocysteine / Mammals / Mice / Molecular Dynamics Simulation / Molecular Sequence Data / multidisciplinary / Protein Structure, Tertiary / S-Adenosylhomocysteine - metabolism / Science / Sequence Alignment / Substrate Specificity