乳酸脱氢酶同工酶的结构适应性
Structural adaptations of lactate dehydrogenase isozymes.
作者信息
Eventoff W, Rossmann M G, Taylor S S, Torff H J, Meyer H, Keil W, Kiltz H H
出版信息
Proc Natl Acad Sci U S A. 1977 Jul;74(7):2677-81. doi: 10.1073/pnas.74.7.2677.
The three-dimensional structures of dogfish M4 (muscle) and pig H4 (heart) lactate dehydrogenase (L-lactate:NAD+ oxidoreductase, EC 1.1.1.27) have been determined and correlated with the amino acid sequences of the dogfish M4, pig M4, pig H4, chicken M4, and chicken H4 lactate dehydrogenase isozymes. These results have been related to the known differences of physicochemical properties between the M and H lactate dehydrogenase isozymes. By far the largest structural alterations occur in the transition between the "apo" and "ternary complex" conformational states of the enzyme rather than between species or isozymes. The major catalytic difference can be explained by a replacement of alanine (in the M chain) with a glutamine (in the H chain) in the vicinity of the binding site of the coenzyme phosphates. The known immunological differentiation of the M and H isozymes is consistent with the differences in their amino acid sequences.
已确定鲨鱼M4（肌肉）和猪H4（心脏）乳酸脱氢酶（L-乳酸：NAD+氧化还原酶，EC 1.1.1.27）的三维结构，并将其与鲨鱼M4、猪M4、猪H4、鸡M4和鸡H4乳酸脱氢酶同工酶的氨基酸序列相关联。这些结果与已知的M型和H型乳酸脱氢酶同工酶之间物理化学性质的差异相关。到目前为止，最大的结构变化发生在酶的“脱辅基”和“三元复合物”构象状态之间的转变，而不是在不同物种或同工酶之间。主要的催化差异可以通过在辅酶磷酸结合位点附近，用谷氨酰胺（在H链中）取代丙氨酸（在M链中）来解释。已知的M型和H型同工酶的免疫分化与它们氨基酸序列的差异一致。
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