Mechanistic studies on PseB of pseudaminic acid biosynthesis: A UDP-N-acetylglucosamine 5-inverting 4,6-dehydratase
作者:James P. Morrison、Ian C. Schoenhofen、Martin E. Tanner
DOI:10.1016/j.bioorg.2008.08.004
日期:2008.12
C-4'', enabling dehydration. The alpha,beta unsaturated ketone intermediate is then reduced by delivery of the hydride to C-6'' and a proton to C-5''. Consistent with this, PseB from C. jejuni has been found to incorporate deuterium into the C-5'' position of product during catalysis in D2O. Likewise, PseB catalyzes solvent isotope exchange into the H-5'' position of product, and eliminates HF from
UDP-N-乙酰氨基葡糖5反转4,6-脱水酶(PseB)是一种独特的糖核苷酸脱水酶,可在UDP-N-乙酰氨基葡糖转化为UDP-2-乙酰氨基2,6-的过程中反转C-5''立体中心。双脱氧-β-1-阿拉伯糖-己糖-4-ulose。PseB催化伪氨基酸的生物合成的第一步,这是空肠弯曲杆菌和幽门螺杆菌鞭毛蛋白的翻译后修饰。建议PseB使用其紧密结合的NADP +氧化C-4''处的UDP-GlcNAc,从而实现脱水。然后,通过将氢化物递送至C-6”并将质子递送至C-5”来还原α,β不饱和酮中间体。与此一致的是,已发现空肠弯曲杆菌的PseB在D2O中催化过程中将氘掺入产物的C-5''位。同样地,PseB催化溶剂同位素交换到产物的H-5''位,并从替代底物UDP-6-脱氧-6-氟-GlcNAc中消除HF。假定的催化残基天冬氨酸126,赖氨酸127和酪氨酸135的突变体严重损害了脱水酶,溶剂同位素交换和HF消除活性。