Rao A S
Arch Microbiol. 1985 Mar;141(2):143-50. doi: 10.1007/BF00423275.
Lysine biosynthetic pathway enzymes of Bacillus brevis ATCC 1068 were studied as a function of stage of development (growth and sporulation). The synthesis of aspartic-2-semialdehyde dehydrogenase (ASA-dehydrogenase), dihydrodipicolinate synthase (DHDPA-synthase), DHDPA-reductase and diaminopimelate decarboxylase (DAP-decarboxylase) was found not to be co-regulated, since lysine was not a co-repressor for these enzymes. Unlike the aspartokinase isoenzymes, the other enzymes of the lysine pathway were not derepressed in thiosine-resistant, lysine-excreting mutants. Thus, the aspartokinase isoenzymes were the key enzymes during growth and regulation of lysine biosynthesis through restriction of L-ASA synthesis via feedback control by lysine on the aspartokinases was therefore suggested. In contrast to other Bacillus species, the levels of the lysine biosynthetic pathway enzymes of strain ATCC 10068 were not derepressed during the change from vegetative growth to sporulation. Two control mechanisms, enabling the observed preferential channelling of carbon for the synthesis of spore-specific diaminopimelic acid (DAP) and dipicolinic acid (DPA) were a) loss of DAP-decarboxylase, b) inhibition of DHDPA-reductase by DPA. Increase in the level of the DAP pool during sporulation, as a consequence of the loss of DAP-decarboxylase, and its relevance to the non-enzymatic formation of DPA has been discussed.
对短短芽孢杆菌ATCC 1068的赖氨酸生物合成途径酶进行了研究，以探讨其作为发育阶段（生长和孢子形成）的函数关系。发现天冬氨酸-2-半醛脱氢酶（ASA脱氢酶）、二氢吡啶二羧酸合酶（DHDPA合酶）、DHDPA还原酶和二氨基庚二酸脱羧酶（DAP脱羧酶）的合成不受共同调控，因为赖氨酸不是这些酶的共阻遏物。与天冬氨酸激酶同工酶不同，赖氨酸途径的其他酶在硫代赖氨酸抗性、赖氨酸分泌突变体中不会去阻遏。因此，天冬氨酸激酶同工酶是生长过程中的关键酶，通过赖氨酸对天冬氨酸激酶的反馈控制来限制L-ASA的合成，从而调节赖氨酸的生物合成。与其他芽孢杆菌属不同，在从营养生长向孢子形成转变过程中，菌株ATCC 10068的赖氨酸生物合成途径酶水平不会去阻遏。有两种控制机制使得观察到的碳优先用于合成孢子特异性二氨基庚二酸（DAP）和吡啶二羧酸（DPA），即：a）DAP脱羧酶的缺失；b）DPA对DHDPA还原酶的抑制。由于DAP脱羧酶的缺失，孢子形成过程中DAP库水平的增加及其与DPA非酶形成的相关性已得到讨论。
