Walker G J, Pulkownik A, Morrey-Jones J G
J Gen Microbiol. 1981 Nov;127(1):201-8. doi: 10.1099/00221287-127-1-201.
Dextranase activity was determined in cell extracts and cell-free filtrates of Streptococcus mutans strains which had been grown in batch culture. Exo-dextranase activity was located chiefly in cell extracts, whereas endo-dextranase was mainly extracellular. Release of endo-dextranase began early in the exponential phase of growth, and ended when the concentration of residual sugar was low. Thus, dextranase expression was associated with rapidly growing cells, the yield of dextranase was increased several fold when the initial concentration of D-glucose in the medium was changed from 0.5% to 2%. The endo-dextranase was not stable at pH 5, and control of the pH of the culture was essential to preserve active dextranase during overnight growth. Strain Ingbritt (serotype c) and serotype d strains were the best dextranase producers; other strains (serotypes a, b, c, e and f) displayed much lower activity. The ability to produce endo-dextranase, and to synthesize alpha-D-glucans with a high proportion of (1 leads to 3)-linked sequences, appeared to be related properties. The possibility is discussed that the release of two enzymes, namely endo-dextranase and the D-glucosyltransferase (GTF-I) that synthesizes (1 leads to 3)-alpha-D-glucan, are factors that contribute to the cariogenicity of S. mutans serotype d.
在分批培养生长的变形链球菌菌株的细胞提取物和无细胞滤液中测定了葡聚糖酶活性。外切葡聚糖酶活性主要存在于细胞提取物中，而内切葡聚糖酶主要存在于细胞外。内切葡聚糖酶的释放始于生长指数期早期，当残留糖浓度较低时结束。因此，葡聚糖酶的表达与快速生长的细胞有关，当培养基中D-葡萄糖的初始浓度从0.5%变为2%时，葡聚糖酶的产量增加了几倍。内切葡聚糖酶在pH 5时不稳定，控制培养物的pH对于在过夜生长期间保持活性葡聚糖酶至关重要。英布里特菌株（血清型c）和血清型d菌株是最好的葡聚糖酶生产者；其他菌株（血清型a、b、c、e和f）的活性要低得多。产生内切葡聚糖酶以及合成具有高比例（1→3）连接序列的α-D-葡聚糖的能力似乎是相关特性。有人讨论了内切葡聚糖酶和合成（1→3）-α-D-葡聚糖的D-葡萄糖基转移酶（GTF-I）这两种酶的释放是导致变形链球菌血清型d致龋性的因素的可能性。
