| Autor: |
Dan Sato, Tomoo Shiba, Tsuyoshi Karaki, Wataru Yamagata, Tomoyoshi Nozaki, Takashi Nakazawa, Shigeharu Harada |
| Jazyk: |
angličtina |
| Rok vydání: |
2017 |
| Předmět: |
|
| Zdroj: |
Scientific Reports, Vol 7, Iss 1, Pp 1-10 (2017) |
| Druh dokumentu: |
article |
| ISSN: |
2045-2322 |
| DOI: |
10.1038/s41598-017-05032-6 |
| Popis: |
Abstract Pyridoxal 5′-phosphate (PLP)-enzymes are essentially involved in amino acid and amine metabolism of a wide variety of organisms. Despite their extensive biochemical studies, there are little evidence and structural data to comprehensively elaborate the catalytic mechanism. We obtained X-ray snapshots of l-methionine γ-lyase from Entamoeba histolytica (EhMGL), a PLP-enzyme catalyzing the γ-elimination reaction of methionine. Here, we suggest a catalytic mechanism of EhMGL by using the X-ray snapshots covering all stages of this multistep catalysis reaction. Initial formation of a Michaelis complex is followed by the migration of double bond from the C4′=Nα–Cα moiety in an intermediate PLP-methionine imine to C4′–Nα=Cα in pyridoxamine 5′-phosphate (PMP)-α,β-dehydromethionine imine without intervention of a putative quinonoid intermediate. The enzyme can facilitate the subsequent γ-elimination of methanethiol by the possible general acid-base catalysis of Tyr108 for the E1cB mechanism, enabling to form the ene-imine C4′–Nα=Cα–Cβ=Cγ structure with the s-cis conformation, which is prerequisite for the non-enzymatic symmetry-allowed suprafacial [1,5]-hydrogen shift to complete the catalytic cycle by releasing α-ketobutyrate. The mechanism based on the X-ray snapshots is consistent with the reactivity of MGL toward methionine analogues. The generality of such a mechanism involving non-enzymatic concerted reaction in other PLP enzymes is discussed. |
| Databáze: |
Directory of Open Access Journals |
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