PDF(Pubmed)
Abstract：
Biosynthesis of atypical angucyclines involves unique oxidative B-ring cleavage and rearrangement reactions, which are catalyzed by AlpJ-family oxygenases, including AlpJ, JadG, and GilOII. Prior investigations established the essential requirement for FADH2/FMNH2 as cofactors when utilizing the quinone intermediate dehydrorabelomycin as a substrate. In this study, we unveil a previously unrecognized facet of these enzymes as cofactor-independent oxygenases when employing the hydroquinone intermediate CR1 as a substrate. The enzymes autonomously drive oxidative ring cleavage and rearrangement reactions of CR1, yielding products identical to those observed in cofactor-dependent reactions of AlpJ-family oxygenases. Furthermore, the AlpJ- and JadG-catalyzed reactions of CR1 could be quenched by superoxide dismutase, supporting a catalytic mechanism wherein the substrate CR1 reductively activates molecular oxygen, generating a substrate radical and the superoxide anion O2 •-. Our findings illuminate a substrate-controlled catalytic mechanism of AlpJ-family oxygenases, expanding the realm of cofactor-independent oxygenases. Notably, AlpJ-family oxygenases stand as a pioneering example of enzymes capable of catalyzing oxidative reactions in either an FADH2/FMNH2-dependent or cofactor-independent manner.
摘要：
非典型angucyclines的生物合成涉及独特的氧化B环裂解和重排反应，由AlpJ家族加氧酶催化，包括AlpJ,JadG,还有吉洛.先前的研究确立了在利用醌中间体脱水abelomycin作为底物时对FADH2/FMNH2作为辅因子的基本要求。在这项研究中,当使用氢醌中间体CR1作为底物时，我们揭示了这些酶作为不依赖辅因子的加氧酶的一个以前未被认识的方面。这些酶自主驱动CR1的氧化环裂解和重排反应，产生的产物与AlpJ家族加氧酶的辅因子依赖性反应中观察到的产物相同。此外，AlpJ-和JadG-催化的CR1反应可以被超氧化物歧化酶猝灭，支持催化机制，其中底物CR1还原活化分子氧，产生底物自由基和超氧阴离子O2·-。我们的发现阐明了AlpJ家族加氧酶的底物控制的催化机理，扩大不依赖辅因子的加氧酶的领域。值得注意的是,AlpJ家族加氧酶是能够以FADH2/FMNH2依赖性或辅因子非依赖性方式催化氧化反应的酶的开创性实例。
