2-Methylisocitrate裂解酶细菌大肠杆菌和丝状真菌曲霉菌nidulans:酶的描述和比较。
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布洛克M,达利D,文本或年代,上W
2-Methylisocitrate裂解酶细菌大肠杆菌和丝状真菌曲霉菌nidulans:酶的描述和比较。
欧元。2001 268年6月,(12):3577 - 86。
- PubMed ID
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11422389 (在PubMed]
- 文摘
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在大肠杆菌和曲霉菌nidulans,丙酸氧化成丙酮酸通过methylcitrate周期。这个周期的最后一步,乳沟2-methylisocitrate 2-methylisocitrate琥珀酸和丙酮酸催化了裂合酶。酶的生物与化学合成threo-2-methylisocitrate化验;erythro-diastereomer并不活跃。2-Methylisocitrate裂合酶大肠杆菌对应PrpB蛋白质的prp操纵子参与丙酸氧化。纯化酶的分子量大约32每单元kDa,低于异柠檬酸裂解酶的细菌来源(约48 kDa)。2-Methylisocitrate裂合酶从a nidulans显示了明显的分子质量每单元66 kDa,几乎等于异柠檬酸裂解酶的相同的有机体。两个2-methylisocitrate裂解酶有本机homotetrameric结构被凝胶排阻层析法。酶显示与异柠檬酸没有可衡量的活动。从250 mM丙酮酸、琥珀酸150毫米和10 microM PrpB,保持酶的活性可以合成立体异构体1%收益。 As revealed by chiral HPLC, the product consisted of a single enantiomer. This isomer is cleaved by 2-methylisocitrate lyases from A. nidulans and E. coli. The PrpB protein reacted with stoichiometric amounts of 3-bromopyruvate whereby the activity was lost and one amino-acid residue per subunit became modified, most likely a cysteine as shown for isocitrate lyase of E. coli. PrpB exhibits 34% sequence identity with carboxyphosphoenolpyruvate phosphonomutase from Streptomyces hygroscopicus, in which the essential cysteine residue is conserved.