BETA-GALACTOSIDASE ACTIVITY AND LACTOSE UTILIZATION IN ASPERGILLUS-NIDULANS
BETA-GALACTOSIDASE ACTIVITY AND LACTOSE UTILIZATION IN ASPERGILLUS-NIDULANS
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DOI：
10.1099/00221287-77-2-471
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发表时间：
1973-01-01
期刊：
影响因子：
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通讯作者：
ROBERTS, CF
中科院分区：
文献类型：
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作者：
FANTES, PA;ROBERTS, CF
以乳糖或半乳糖为碳源培养构巢曲霉菌丝体，β-半乳糖苷酶活性至少可提高30倍。研究了生长条件对该酶活性形成的影响，并对该酶进行了部分表征：分子量分别为120000和450000的两种蛋白质具有β-半乳糖苷酶活性;目前的证据表明，这两种蛋白质是同一多肽的不同聚集体;描述了一种突变体lac 150，它在乳糖上生长不良，缺乏β-半乳糖苷酶活性。这两个性状是由两个不连锁的基因决定的，并独立表达。这表明存在乳糖利用的替代（和未知）模式。虽然β-半乳糖苷酶活性不是菌丝在乳糖上生长所必需的，但它是以乳糖为唯一碳源的分生孢子萌发所必需的，不能产生β-半乳糖苷酶活性的突变体可分为dbgaA、B和C三个遗传群，所有这些突变体都能以乳糖为唯一碳源正常生长。bgaA位点的一个突变体形成不耐热的β-半乳糖苷酶，推测是结构基因损伤。
When mycelia ofAspergillus nidulansare grown with lactose or galactose as the carbon source,β-galactosidase activity is induced at least 30-fold. The effect of growth conditions on the formation of the activity was investigated.The enzyme has been partially characterized: two proteins with molecular weights near 120000 and 450000 haveβ-galactosidase activity; present evidence suggests that these are different aggregates of the same polypeptide.A mutant,lac150, is described which grows poorly on lactose and lacksβ-galactosidase activity. These two characters are determined by two unlinked genes and independently expressed. This demonstrates the existence of an alternative (and unknown) mode of lactose utilization. Althoughβ-galactosidase activity is not required for mycelial growth on lactose, it is essential for germination of conidia with lactose as the sole carbon source.Mutants unable to formβ-galactosidase activity fall into three genetic groups designatedbgaA, BandC.All these mutants grow normally with lactose as sole carbon source. One mutant at thebgaAlocus forms a heat-labileβ-galactosidase and is presumably a structural gene lesion.