ROLE OF ALPHA-LACTALBUMIN AND A PROTEIN IN LACTOSE SYNTHETASE - A UNIQUE MECHANISM FOR CONTROL OF A BIOLOGICAL REACTION
ROLE OF ALPHA-LACTALBUMIN AND A PROTEIN IN LACTOSE SYNTHETASE - A UNIQUE MECHANISM FOR CONTROL OF A BIOLOGICAL REACTION
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DOI：
10.1073/pnas.59.2.491
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发表时间：
1968-01-01
影响因子：
11.1
通讯作者：
HILL, RL
中科院分区：
文献类型：
--
作者：
BREW, K;VANAMAN, TC;HILL, RL
这些研究旨在明确 A 蛋白和 α-LA [乳白蛋白] 在乳糖合成酶中的作用。分离的A蛋白是UDP-半乳糖：N-乙酰基-葡糖胺半乳糖基转移酶，其催化以下反应：UDP-半乳糖+N-乙酰基-D-葡糖胺[向前箭头]N-乙酰基乳糖胺+UDP。在正常测定条件下，α-LA抑制该反应并允许在葡萄糖存在下合成乳糖。因此，α-LA改变了半乳糖基转移酶的底物(受体)特异性，从NAG[N-乙酰基-D-葡糖胺]到葡萄糖。这似乎是迄今为止不归因于蛋白质的作用并且α-LA可以被称为“特异性”蛋白质。它影响底物特异性变化的机制似乎很复杂，但它可能代表了一种新型的生物反应分子控制。
The studies were designed to define the roles of the A protein and [alpha]-LA [lactalbumin] in lactose synthetase. The separated A protein was a UDP-galactose : N-acetyl-glucosamine galactosyltransferase which catalyzes the following reaction: UDP-galactose + N-acetyl-D-glucosamine[forward arrow]N-acetyllactosamine + UDP. Under normal assay conditions, [alpha]-LA inhibits this reaction and allows synthesis of lactose in the presence of glucose. Thus, the [alpha]-LA modifies the substrate (acceptor) specificity of a galactosyltransferase from NAG [N-acetyl-D-glucosamine] to glucose. This appears to be a role hitherto not ascribed to a protein and [alpha]-LA may be termed a "specifier" protein. The mechanism by which it effects a change in substrate specificity appears to be complex, but it is possible that it represents a new type of molecular control of a biological reaction.