Graduate School of Biological Sciences, Nara Institute of Science and Technology (NAIST), Ikoma, Nara 630-0192, Japan.
Biochem Biophys Res Commun. 2013 Feb 8;431(2):176-80. doi: 10.1016/j.bbrc.2012.12.142. Epub 2013 Jan 9.
Ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) and RuBisCO-like protein (RLP) from Bacillus subtilis catalyze mechanistically similar enolase reactions. Both enzymes require carbamylation of the ε-amino group of the active site lysine during activation to generate the binding site of the essential Mg(2+) ion. His267 forms a possible hydrogen bond with the carbamate of the active site Lys176 in B. subtilis RLP. This active site histidine is completely conserved in RLPs and RuBisCO. H267Q, H267N and H267A mutant enzymes required higher CO(2) concentrations for maximal activity than wild-type enzyme, suggesting that the histidine is involved in high affinity for activator CO(2) in Bacillus RLP. These mutations showed weak effects on the catalysis of RLP, whereas this residue is reportedly essential for catalysis in RuBisCO but is not involved in the carbamylation. The different functions of the active site histidine in RLP and RuBisCO are discussed.
核酮糖-1,5-二磷酸羧化酶/加氧酶（RuBisCO）和枯草芽孢杆菌中的 RuBisCO 样蛋白（RLP）催化机制相似的烯醇化反应。这两种酶在激活过程中都需要将活性位点赖氨酸的ε-氨基进行氨甲酰化，以生成必需的 Mg2+离子的结合位点。枯草芽孢杆菌 RLP 中的 His267 可能与活性位点 Lys176 的氨基甲酸盐形成氢键。该活性位点组氨酸在 RLPs 和 RuBisCO 中完全保守。与野生型酶相比，H267Q、H267N 和 H267A 突变酶需要更高的 CO2 浓度才能达到最大活性，这表明组氨酸参与了枯草芽孢杆菌 RLP 中激活剂 CO2 的高亲和力。这些突变对 RLP 的催化作用影响较弱，而据报道该残基对 RuBisCO 的催化作用至关重要，但不参与氨甲酰化。讨论了活性位点组氨酸在 RLP 和 RuBisCO 中的不同功能。
