肌醇和磷脂酰肌醇在酵母菌蔗糖酶分泌调控中的作用

Inositol-mediated invertase secretion in Saccharomyces sp. W4 In this study, the effects of inositol addition on invertase secretion in Saccharomyces sp. W4 were examined. We found that invertase secretion in this strain was repressed when the completely synthetic medium lacking exogenous inositol contains more than 0.2 (w/v) glucose; However, when the yeast cells were grown in the same medium plus inositol, repression of invertase secretion in this strain occurred only at glucose concentrations higher than 2.0% (w/v). Furthermore, when sucrose was used as carbon source, increased invertase activity was observed in the presence of inositol. Repression occurred only at sucrose concentrations above 4.0% (w/v). More cell growth occurred and less residual reducing sugar was left in the inositol-containing medium than in the inositol-deficient medium as glucose or sucrose concentration was increased. These results demonstrate that inositol supplemetation could derepress invertase secretion and cell growth in this yeast strain to some extent and sucrose was more suitable for invertase production than glucose. When the repressed yeast cells were transferred to the synthetic medium with low concentration glucose or sucrose, they could synthesize more extracellular invertase in the presence of inositol than in the absence of inositol..2) Inositol and phosphatidylinositol-mediated invertase.secretion in Schizosaccharomyces pombe.In this study, the effects of inositol addition on invertase secretion, biosynthesis of mRNA encoding secreted invertase and phosphatidylinositol (PI) biosynthesis in Schizosaccharomyces pombe were examined. We found that specific invertase activity was at its maximum when the concentration of added inositol reached 800 mg/100ml in the synthetic medium containing 2.0% (w/v) sucrose. However, cell growth was steadily increased as inositol concentrations were increased from 0 to 1000 mg/100ml. When the concentration of added inositol was 100 mg/100ml in the synthetic medium, repression of invertase secretion occurred at sucrose concentration higher than 0.5% (w/v). However, when S. pombe was cultured in the synthetic medium containing 800 mg/100ml, repression of invertase secretion occurred only at sucrose concentrations above 2.0% (w/v). Less residual reducing sugar was left in the 800 mg /100 ml inositol-containing medium than in the 100 mg /100ml inositol-containing medium as sucrose concentration was increased. More mRNA encoding secreted invertase was detected in cells grown in the 800 mg /100ml inositol-containing medium (2.0% sucrose) than in those grown in the 100 mg /100ml inositol-containing medium. These results demonstrate that higher concentration of added inositol in the synthetic medium could derepress invertase secretion and INV +gene expression in S. pombe. .PI content of the yeast cells grown in the synthetic medium with 800 mg/100ml of inositol was higher than that of the yeast cells grown in the same medium with 100 mg/100ml of inositol. This means that PI may be involved in derepression of invertase secretion.3) The Effects of INO1 Gene Expression in Schizosaccharomyces pombe on Invertase Secretion and Phosphoinositol(PI) Synthesis.In this study, Schizosaccharomyces pombe , a natural inositol auxotroph,was transformed with the two plasmids, pADH-INO and pSPIN-22, which contain a Pichia pastoris INO1 gene encoding inositol synthase. The two transformants are named as Sch.p944 and Sch.p1025, respectively. The results confirmed that the plasmids in the cells could replicate autonomously and confer inositol prototrophy to the Schizosaccharomyces pombe, but the rate and the amount of inositol synthesized in Sch.P944 was faster and more than that in Sch.P1025. Plasmid loss experiments showed that the rate of plasmid loss in Sch.p944 was about 3.3 % and that in Sch.p1025 was about 6.9% after 40 h fermentation. Comparison of the derepression of invertase expression and cell growth between the two transformants showed that the cell growth and the specific invertase activity are af

利用阻遏和去阻遏条件下的酵母细胞研究添加肌醇对蔗糖酶分泌、分泌小泡在细胞中的量与分布和蔗糖酶基因转录的影响.同时还研究磷脂酰肌醇及其衍生物4，5-二磷酸磷脂酰肌醇含量和蔗糖酶基因转录的相互关系以便弄肌醇和磷脂酰肌醇对蔗糖酶分泌的调控作用。这一研究对于提高酵母菌蔗糖的产量、了解膜磷脂和胞外酶分泌的关系有重要的意义。