Hitchcock M H, Hodgson B
Biochim Biophys Acta. 1976 Sep 14;445(2):350-63. doi: 10.1016/0005-2744(76)90089-9.
Two aspartokinase (ATP:L-aspartate 4-phosphotrasferase, EC 2.7.2.4) enzyme activities have been identified and partially purified from Bacillus brevis. Aspartokinase I is subject to both inhibition and repression by lysine, and has a molecular weight in the region of 110 000. Aspartokinase II is a lysine-stabilised enzyme, inhibited multivalently by lysine plus theonine and has a molecular weight in the region of 95 000. This attern of aspartokinase activity has not been described previously and is unusual in that one end product (lysine) regulates two isoenzymes catalysing the first reaction of a branced biosynthetic pathway. In the absence of lysine, aspartokinase II changes to a more unstable non-inhibitable enzyme. Both enzymes are stabilised by sulphydryl reducing agents and have similar affinities for ATP, aspartate and lysine. However, there is no evidence for a view that they are products of a common gene. Problem concerned with the regulation of aspartokinase activities in Bacillus species are discussed.
已从短短芽孢杆菌中鉴定并部分纯化出两种天冬氨酸激酶（ATP：L-天冬氨酸4-磷酸转移酶，EC 2.7.2.4）的酶活性。天冬氨酸激酶I受赖氨酸的抑制和阻遏作用，分子量约为110000。天冬氨酸激酶II是一种赖氨酸稳定型酶，受赖氨酸加苏氨酸的多价抑制，分子量约为95000。这种天冬氨酸激酶活性模式以前未曾描述过，而且不同寻常之处在于，一种终产物（赖氨酸）调节两种同工酶，它们催化一条分支生物合成途径的第一步反应。在没有赖氨酸的情况下，天冬氨酸激酶II转变为一种更不稳定的、不可抑制的酶。两种酶都可被巯基还原剂稳定，并且对ATP、天冬氨酸和赖氨酸具有相似的亲和力。然而，没有证据支持它们是一个共同基因产物的观点。文中讨论了与芽孢杆菌中天冬氨酸激酶活性调节有关的问题。
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