Saccharomyces酵母におけるα-Glucosidase生産と構成遺伝子の関係について(I)

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Genetic analysis of a diploid hybrid (D-346) has revealed that two or more dominant genes for maltose and three (X, Y_1 and Y_3) for α-methyl-glucoside are involved in the genotype; the gene X in combination either with Y_1 or with Y_2 enables α-methyl-glucoside fermentation.Using four haploid clones (A, B, C and D) derived from an ascus of this strain, a survey was made of α-methyl-glucosidase activities in extracts from induced cells. The results indicated the multiplicity of maltases and the existence of another enzyme active in hydrolyzing α-methyl-glucoside; the latter enzyme was presumed to be active in hydrolyzing isomaltose and α-phenyl-glucoside, but not maltose.The permeability of cells to maltose and to α-methyl-glucoside was tested by our improved inulin method, and it was shown that all the four clones were permeable to maltose, but two clones impermeable to α-methyl-glucoside, although the extracts obtained from these α-methyl-glucoside non-fermenters manifested activity in splitting α-methyl-glucoside.Reflecting the results of enyzme studies and of permeation tests in connection with the genotypic composition of these clones, it is concluded that permeability to α-methyl-glucoside is controlled by the gene X, and that the other two genes, Y_1 and Y_2,control enzyme formation, although the existence of another undetermined factor concerned with the inducibility of so-called α-methyl-glucosidase was presumed from the results of experiments in which maltose was used as inducer.Purified maltase preparation (from cells of Saccharomyces cerevisiae) free from so-called α-methyl-glucosidase could be analyzed into two enzyme fractions (maltase 1 and 2) by means of zone electrophoresis, each being invariable in activity ratios in splitting maltose, α-methyl-glucoside and α-phenyl-glucoside, but different in relative specificity from each other. Highly purified enzyme preparation of so-called α-methyl-glucosidase having no maltase activity was also obtained from cells of S. cerevisiae. Based on activity distribution in the effluent fractions of resin chromatography, and invariable activity ratios in splitting isomaltose, panose etc., the preparation is considered to contain a single α-glucosidase so far as the substrates tested are concerned. Isomaltose is hydrolyzed into glucose, panose into glucose and maltose; no other product is detectable. Optimum pH is ca. 6.8.We have recommended here to adopt the name "isomaltase" to this enzyme instead of α-methyl-glucosidase since α-methyl-glucoside is a common substrate of maltase and "isomaltase" while isomaltose is a natural substrate hydrolyzable not by maltase but by this enzyme.
社団法人日本生物工学会の論文
1959-05-15

Saccharomyces酵母におけるα-Glucosidase生産と構成遺伝子の関係について(I)

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