红曲AS 3．3491葡萄糖淀粉酶生物合成的调节

红曲 Monascus AS 3.978的变异株 AS 3.3491曾是葡萄糖淀粉酶的工业生产菌株。本文报告的实验结果表明该菌株的葡萄糖淀粉酶是构成酶,它的形成受降解物阻遏的调控。AS 3.3491葡萄糖淀粉酶形成的时间过程属典型的产物形成与生长呈负相关的类型,即菌丝体生长停止后酶才开始大量形成。从培养基中除去过量易利用碳源可使葡萄糖淀粉酶形成消阻遏。各种可利用碳源以低浓度分别加到洗涤的菌丝体悬浮液中都能促进葡萄糖淀粉酶的形成,其中蜜二糖和半乳糖的促进作用最甚。在限制生长的条件下,即向洗涤菌丝悬浮液连续缓慢供给低浓度葡萄糖,则在整个培养过程中,葡萄糖淀粉酶的活力稳步上升,不需要任何诱导物,并且比酶形成值达到蜜二糖培养基的水平。因此,高浓度葡萄糖阻遏葡萄糖淀粉酶形成,但低浓度葡萄糖却促进酶的形成。

THE REGULATION OF GLUCOAMYLASE SYNTHESIS IN MONASCUS AS 3.3491

Monascus sp.AS 3.3491 is a glucoamylase producing strain.The results obtained suggested that glucoamylase in this strain is a constitutive enzyme and its formation is controlled by so-called catabolite repression. The time course of the glucoamylase formation exhibited a typical feature of the pro- cess of non-growth associated product formation,i.e.,the enzyme accumulation in the me- dium became remarkable after growth ceased.The enzyme formation was derepressed by removing the excess readily utilizable carbon source from the medium.The addition of all the tested usable carbon sources to the washed mycelium at a low concentration stimulated the glucoamylase production.Of them,melibiose and galactose had the strongest effect. It was found that under conditions of restricted growth by slow feeding of low concen- tration of glucose to washed mycelium suspension,the glucoamylase activity increased stea- dily during the whole incubation with no need of any inducer and its specific enzyme for- mation was the same with that in melibiose medium.Therefore,the high concentration of glucose repressed the glucoamylase formation while the low concentration of glucose stimu- lated the enzyme formation.