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Publication Abstract from PubMed

l-Methionine gamma-lyse (MGL), a pyridoxal 5'-phosphate-dependent enzyme, catalyzes the alpha,gamma-elimination of l-methionine (l-Met) and l-homocysteine (l-Hcy) to produce alpha-keto acids, thiols, and ammonia. Previously, various mutant enzymes of Pseudomonas putida MGL (PpMGL) were prepared to identify a homocysteine (Hcy)-specific enzyme that would assist the diagnosis of homocystinuria. Among the mutat enzymes the Q349S mutant exhibited high degradation activity toward l-Hcy. In the present study, PpMGL Q349S was characterized; the results suggested that it could be applied to determine the amount of l-Hcy. Compared to the wild-type PpMGL, specific activities of the Q349S mutant with l-Hcy and l-Met were 1.5 and 0.7 times, respectively. Additionally, we confirmed that l-Hcy in plasma samples could be accurately detected using the Q349S mutant by preincubating it with cysteine desulfurase (CsdA). Furthermore, we determined the X-ray crystal structure of PpMGL Q349S l-Met or l-Hcy complexes Michaelis complex, germinal diamine, and external aldimine at 2.25-2.40 A. These 3D structures showed that the interaction partner of the beta-hydroxyl group of Thr355 in the wild-type PpMGL was changed to the carboxyl group of the Hcy-PLP external aldimine in the Q349S mutant. The interaction of Ser349 and Arg375 was different between l-Met and l-Hcy recognition, indicating that it was important for the recognition of the carboxyl group of the substrate.

Characterization and application of l-methionine gamma-lyase Q349S mutant enzyme with an enhanced activity toward l-homocysteine.,Okawa A, Handa H, Yasuda E, Murota M, Kudo D, Tamura T, Shiba T, Inagaki K J Biosci Bioeng. 2022 Mar;133(3):213-221. doi: 10.1016/j.jbiosc.2021.11.008. Epub, 2021 Dec 23. PMID:34953671^[1]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.