Yeggy J P, Stahly D P
Can J Microbiol. 1980 Dec;26(12):1386-91. doi: 10.1139/m80-231.
Homoserine dehydrogenase in dialyzed cell extracts of Bacillus subtilis 168 was studied, particularly with regard to inhibition, repression, and level of activity as a function of stage of development (growth and sporulation). It was assayed in the "forward direction" using L-aspartic semialdehyde and NADPH as substrates. Of the potentials inhibitors tested, only cysteine and NADP were found to be effective. Both L- and D-cysteine were equally effective. Therefore, the physiological significance of cysteine as an inhibitor is somewhat questionable. Amino acids involved in repression of homoserine dehydrogenase included methionine, isoleucine, possibly threonine, and one or more unidentified components of Casamino acids. The specific activity of homoserine dehydrogenase was highest during the exponential phase of growth and declined steadily during the stationary phase of growth. The low specific activity during late sporulation may favor preferential funnelling of L-aspartic semialdehyde into the lysine pathway, where it is needed for synthesis of large amounts of dipicolinic acid and diaminopimelic acid.
对枯草芽孢杆菌168透析细胞提取物中的高丝氨酸脱氢酶进行了研究，尤其研究了其抑制作用、阻遏作用以及作为发育阶段（生长和孢子形成）函数的活性水平。使用L-天冬氨酸半醛和NADPH作为底物，以“正向”方式对其进行测定。在所测试的潜在抑制剂中，仅发现半胱氨酸和NADP有效。L-半胱氨酸和D-半胱氨酸的效果相同。因此，半胱氨酸作为抑制剂的生理意义有些值得怀疑。参与高丝氨酸脱氢酶阻遏的氨基酸包括蛋氨酸、异亮氨酸、可能还有苏氨酸以及酪蛋白氨基酸中的一种或多种未鉴定成分。高丝氨酸脱氢酶的比活性在生长指数期最高，在生长稳定期稳步下降。孢子形成后期的低比活性可能有利于L-天冬氨酸半醛优先进入赖氨酸途径，在该途径中合成大量吡啶二羧酸和二氨基庚二酸需要L-天冬氨酸半醛。
