产甘油假丝酵母甘油代谢关键酶的研究

本文对产甘油假丝酵母的甘油代谢关键酶进行了研究,发现产甘油假丝酵母同化甘油能力极弱,少量葡萄糖明显改善其同化甘油的能力;线粒体3磷酸甘油脱氢酶受3磷酸甘油的强烈诱导,受葡萄糖代谢的阻遏。在甘油发酵过程中,产甘油假丝酵母胞浆3磷酸甘油脱氢酶酶活处于较高水平并在36h和60h时出现两次酶活高峰,其中第一次酶活峰值水平决定产甘油假丝酵母的甘油合成和积累水平,成为甘油高速积累期(18～48h)甘油合成的关键性的限速酶。在甘油发酵18～48h内,3磷酸甘油酯酶的酶活处于高水平,并在36h时出现酶活峰值;处于缓慢甘油积累阶段的48～72h间,3磷酸甘油酯酶已处于低水平表达,此时,3磷酸甘油酯酶则成为甘油合成的限速酶。产甘油假丝酵母稳定并高表达其胞浆3磷酸甘油脱氢酶基因并且其所表达的3磷酸甘油酯酶酶活远高于胞浆3磷酸甘油脱氢酶这一特征是其高产甘油根本所在。

THE KEY ENZYMES OF METABOLISMS OF GLYCEROL IN CANDIDA GLYCEROLGENESIS

The specific enzymes for glycerol formation and dissimilation in Candida glycerolgenesis were studied. C.glycerolgenesis hardly assimilated glycerol without glucose and a little amount of glucose remarkably stimulated this dissimilation pathway and the activity and expression of mitochondrial glycerol 3 phosphate dehydrogenase was induced strongly by glycerol 3 phosphate and repressed by glucose metabolism. During glycerol production fermented by C.glycerolgenesis , the activity of cytoplasmic glycerol 3 phosphate dehydrogenase maintained at a higher level and existed two peaks of activity, which appeared at 36h and 60h, respectively. The activity level of the first activity peak determines glycerol productivity and becomes a key enzyme of glycerol formation. The activity of glycerol 3 phosphatase maintained at a higher level just between 18h and 48h and appeared on paek activity at 36h. In that period, the activity of glycerol 3 phosphatase was up to more than two times of cytoplasmic glycerol 3 phosphate dehydrogenase and that was inosculated with the phase of rapid accumulation of glycerol during glycerol production by C.glycerolgenesis . In the phase of slowly accumulation of glycerol between 48h and 72h, the activity of glycerol 3 phosphatase decreased below that of cytoplasmic glycerol 3 phosphate dehydrogenase. So, cytoplasmic glycerol 3 phosphate dehydrogenase is a key enzyme of glycerol formation in the phase of rapid accumulation of glycerol and glycerol 3 phosphatase becomes a more effective factor after glycerol fermentation reached into slowly accumulation phase. In a conclusion, it is a fundamental for C.glycerolgenesis over producing high level of glycerol that its cytoplasmic glycerol 3 phosphate dehydrogenase maintains at high activity and the activity of glycerol 3 phosphatase is much higher than that of cytoplasmic glycerol 3 phosphate dehydrogenase.