Mechanistic Diversity in the RuBisCO Superfamily: RuBisCO from Rhodospirillum rubrum Is Not Promiscuous for Reactions Catalyzed by RuBisCO-like Proteins
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- 作者：Benjamin P. E. Warlick ; Heidi J. Imker ; Jaya Sriram ; F. Robert Tabita ; John A. Gerlt
- 刊名：Biochemistry
- 出版年：2012
- 出版时间：November 27, 2012
- 年：2012
- 卷：51
- 期：47
- 页码：9470-9479
- 全文大小：486K
- 年卷期：v.51,no.47(November 27, 2012)
- ISSN：1520-4995
文摘
d-Ribulose 1,5-bisphosphate carboxylase/oxygenases (RuBisCOs) are promiscuous, catalyzing not only carboxylation and oxygenation of d-ribulose 1,5-bisphosphate but also other promiscuous, presumably nonphysiological, reactions initiated by abstraction of the 3-proton of d-ribulose 1,5-bisphosphate. Also, RuBisCO has homologues that do not catalyze carboxylation; these are designated RuBisCO-like proteins or RLPs. Members of the two families of RLPs catalyze reactions in the recycling of 5鈥?methylthioadenosine (MTA) generated by polyamine synthesis: (1) the 2,3-diketo-5-methylthiopentane 1-phosphate (DK-MTP 1-P) 鈥渆nolase鈥?reaction in the well-known 鈥渕ethionine salvage鈥?pathway in Bacillus sp. and (2) the 5-methylthio-d-ribulose 1-phosphate (MTRu 1-P) 1,3-isomerase reaction in the recently discovered 鈥淢TA-isoprenoid shunt鈥?that generates 1-deoxy-d-xylulose 5-phosphate for nonmevalonate isoprene synthesis in Rhodospirillum rubrum. We first studied the structure and reactivity of DK-MTP 1-P that was reported to decompose rapidly [Ashida, H., Saito, Y., Kojima, C., and Yokota, A. (2008) Biosci., Biotechnol., Biochem. 72, 959鈥?67]. The 2-carbonyl group of DK-MTP 1-P is rapidly hydrated and can undergo enolization both nonenzymatically and enzymatically via the small amount of unhydrated material that is present. We then examined the ability of RuBisCO from R. rubrum to catalyze both of the RLP-catalyzed reactions. Contrary to a previous report [Ashida, H., Saito, Y., Kojima, C., Kobayashi, K., Ogasawara, N., and Yokota, A. (2003) Science 302, 286鈥?90], we were unable to confirm that this RuBisCO catalyzes the DK-MTP 1-P 鈥渆nolase鈥?reaction either in vitro or in vivo. We also determined that this RuBisCO does not catalyze the MTRu 1-P 1,3-isomerase reaction in vitro. Thus, although RuBisCOs can be functionally promiscuous, RuBisCO from R. rubrum is not promiscuous for either of the known RLP-catalyzed reactions.