Aiba S I
Department of Organic Materials, National Institute of Materials and Chemical Research, Ibaraki, Japan.
Int J Biol Macromol. 1993 Aug;15(4):241-5. doi: 10.1016/0141-8130(93)90044-m.
The digestibility of partially N-acetylated chitosans by microbial chitinases was investigated in view of the distribution pattern of N-acetyl groups along the polysaccharide chain. Partially N-acetylated chitosans are classified into two groups; moderately N-deacetylated chitosans (MDC) with 10-30% acetyl content obtained by heterogeneous N-deacetylation of chitin and partially N-acetylated chitosans (PAC-H) with 20-70% acetyl content prepared by homogeneous N-acetylation of highly N-deacetylated chitosans (HDC). MDC have some blocks of N-acetyl-D-glucosamine (GlcNAc) sequences but PAC-H are random-type copolymers of GlcNAc and D-glucosamine. The apparent Km values of Streptomyces griseus chitinase were 0.14 g l-1 for 30% N-acetylated MDC and 0.16 g l-1 for 30% N-acetylated PAC-H. The Km values decreased with increased N-acetylation but the values for both MDC and PAC-H with similar acetyl content were almost the same. The chitinase from S. griseus could not distinguish the difference between block and random distributions of GlcNAc. The chitinases from Bacillus sp. and Bacillus sp. PI-7S also hydrolysed MDC and PAC-H in the same manner. From these results we conclude that sequences of GlcNAc are not necessary for recognition by these chitinases in contrast to lysozyme.
鉴于N-乙酰基沿多糖链的分布模式，研究了微生物几丁质酶对部分N-乙酰化壳聚糖的消化率。部分N-乙酰化壳聚糖分为两组；通过几丁质的非均相N-脱乙酰化获得的乙酰含量为10%-30%的中度N-脱乙酰化壳聚糖（MDC），以及通过高度N-脱乙酰化壳聚糖（HDC）的均相N-乙酰化制备的乙酰含量为20%-70%的部分N-乙酰化壳聚糖（PAC-H）。MDC具有一些N-乙酰-D-葡萄糖胺（GlcNAc）序列块，但PAC-H是GlcNAc和D-葡萄糖胺的无规型共聚物。灰色链霉菌几丁质酶对30%N-乙酰化MDC的表观Km值为0.14 g l-1，对30%N-乙酰化PAC-H的表观Km值为0.16 g l-1。Km值随N-乙酰化程度的增加而降低，但乙酰含量相似的MDC和PAC-H的值几乎相同。灰色链霉菌的几丁质酶无法区分GlcNAc的嵌段分布和无规分布之间的差异。芽孢杆菌属和芽孢杆菌属PI-7S的几丁质酶也以相同的方式水解MDC和PAC-H。从这些结果我们得出结论，与溶菌酶不同，这些几丁质酶识别时GlcNAc序列不是必需的。
