H-2-FORMING N5,N10-METHYLENETETRAHYDROMETHANOPTERIN DEHYDROGENASE FROM METHANOBACTERIUM-THERMOAUTOTROPHICUM - STUDIES OF THE CATALYTIC MECHANISM OF H-2 FORMATION USING HYDROGEN ISOTOPES
H-2-FORMING N5,N10-METHYLENETETRAHYDROMETHANOPTERIN DEHYDROGENASE FROM METHANOBACTERIUM-THERMOAUTOTROPHICUM - STUDIES OF THE CATALYTIC MECHANISM OF H-2 FORMATION USING HYDROGEN ISOTOPES
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DOI：
10.1111/j.1432-1033.1993.tb17657.x
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发表时间：
1993-02-15
期刊：
影响因子：
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通讯作者：
THAUER, RK
中科院分区：
文献类型：
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作者：
SCHWORER, B;FERNANDEZ, VM;THAUER, RK
N5，N-10-亚甲基四氢甲烷蝶呤脱氢酶是一种在产甲烷古菌中发现的新型氢酶。它催化N5，N-10-亚甲基四氢甲蝶呤（CH 2 = H4 MPT）可逆转化为N5，N-10-亚甲基四氢甲蝶呤（CH = H4 MPT）和二氢; CH 2 = HMPT + H+半箭头右半箭头左半箭头CH = HMPT+ + H-2; Δ-度' = + 5.5 kJ/mol。在下面的研究中，在实验中研究了H-2、HD和D2的形成，其中CH 2 = H4 MPT的亚甲基或水被氘标记。在CD 2 = H4 MPT和H2O的情况下，在所有测试的pH下，反应开始后立即形成的二氢由约50%的HD和50%的H-2组成。在CH 2 = HMPT和D2 O的情况下，在pD 5.7时产生的二氢由约50% HD和50% D组成，在pD 7.0时产生的二氢由约85% HD和15% D2组成。有证据表明，该酶催化CH = H4 MPT+依赖的同位素交换HD和H2O之间和HD和D2 O之间，产生H-2和D2，分别。旨在解释这些发现的催化机制进行了讨论。
H-2-forming N5,N-10-methylenetetrahydromethanopterin dehydrogenase is a novel hydrogenase found in most methanogenic archaea. It catalyzes the reversible conversion of N5,N-10-methylenetetrahydromethanopterin (CH2 = H4MPT) to N5,N-10-methenyltetrahydromethanopterin (CH = H4MPT) and dihydrogen; CH2 = HMPT + H+ half arrow right over half arrow left CH = HMPT+ + H-2; DELTAG-degrees' = + 5.5 kJ/mol. In the following investigation, the formation of H-2, HD and D2 was studied in experiments in which either the methylene group of CH2 = H4MPT or water were deuterium labelled. In the case of CD2 = H4MPT and H2O, the dihydrogen formed immediately after the start of the reaction was composed of approximately 50% HD and 50% of H-2 at all pH tested. In the case of CH2 = HMPT and D2O, the dihydrogen generated was composed of approximately 50% HD and 50% D, at pD 5.7 and of approximately 85% HD and 15% D2 at pD 7.0. Evidence is presented that the enzyme catalyzes a CH = H4MPT+-dependent isotopic exchange between HD and H2O and between HD and D2O, yielding H-2 and D2, respectively. A catalytic mechanism aimed to explain these findings is discussed.