摘要：
Genes related to 2,3-butanediol synthesis form a bud operon in Klebsiella pneumoniae. BudB encodes ac etyllactate synthase and budC encodes butanediol dehydrogenase. In addition to the genes in the bud manipulation, ilvB and ilvI also encode the acetylactate synthase in the synthesis pathway of valine, and three dehydrogenases of dhaD, gldA and acyI are reported to have the activity of butanediol dehydrogenase. However, the role of these en zymes on 2,3-butanediol synthesis are not full clear. In this report, mutants of budB, ilvB and ilvI and a four gen e mutant kp-ΔbudC-ΔdhaD-ΔgldA-ΔacyI were constructed. The physical characteristics of these mutants were tested in batch fermentation. ilvB and ilvI mutation have no distinct effect to 2,3-butanediol synthesis, however, kp-Δbud B totally lost the ability to synthesis 2,3-butaneidol, it is shown that the enzyme protein of budB is the only funct ional acetylactate synthase in 2, 3-butanediol synthesis pathway. 2,3-butanediol producted by kp-ΔbudC-ΔdhaD-Δgld A-ΔacyI was decreased comparing with that of kp-ΔbudC, but it was still synthesized. The results showed that the enzyme protein encoded by dhaD, gldA and acyI was weak in the synthesis of 2, 3-butanediol, and there were m any types of alcohol dehydrogenases in the cell with the function of butanediol dehydrogenase.%克雷伯肺炎杆菌2,3-丁二醇合成相关基因形成bud操纵子,其中budB编码乙酰乳酸合成酶,budC编码丁二醇脱氢酶.除了bud操纵子中的基因外,在缬氨酸合成途径中ilvB和ilvI也编码乙酰乳酸合成酶,dhaD、gldA和acyI三个脱氢酶都报道具有丁二醇脱氢酶活性.但是这些基因编码的酶蛋白对菌株合成2,3-丁二醇的贡献并不清楚.本文分别构建了budB、ilvB、ilvI单突变株,和kp-ΔbudC-ΔdhaD-ΔgldA-Δacyl四基因突变株,通过批次发酵实验对这些菌株的生理特性进行了研究.结果显示ilvB和ilvI基因突变对于2,3-丁二醇合成无明显影响,而budB突变株丧失2,3-丁二醇合成能力,表明 budB 编码的酶蛋白是2,3-丁二醇合成途径中唯一的功能性乙酰乳酸合成酶.kp-ΔbudC-ΔdhaD-ΔgldA-Δacyl四基因缺失突变株合成2,3-丁二醇能力相较于kp-ΔbudC有所下降,但仍然能合成2,3-丁二醇,表明dhaD,gldA和acyI编码的酶蛋白对于2,3-丁二醇合成贡献微弱,同时表明细胞中具有丁二醇脱氢酶功能的醇脱氢酶种类较多.
