Walton D J, Jordan D D
Department of Biochemistry, Queen's University, Kingston, Ontario.
Carbohydr Res. 1988 Feb 1;172(2):267-74. doi: 10.1016/s0008-6215(00)90860-7.
The order of enzymic incorporation of O-methyl groups into the O-methyl-D-glucose-containing polysaccharide (MGP) of Mycobacterium smegmatis, 3MG(J)----G(I)----G(H) ----G(G)----6MG(F)----(GMG)9(E)----[G(L)----G(D)]----G(C) ----[G(K)----G(B)]----G(A)----Ga, where G is D-glucose, 3MG is 3-O-methyl-D-glucose, 6MG is 6-O-methyl-D-glucose, and Ga is D-glyceric acid, was studied by incubating cultures of M. smegmatis with L-[3H-Me]methionine for various times. MGP was then extracted from the cells, and relative radioactivities of residues D, (E + F)average and J, or of D, E average, F, and J, were determined. Tritium-labelling of these residues increased in the reducing-to-nonreducing residue direction, the steepness of the gradient becoming more shallow with increasing incubation time. The results are consistent with a biosynthetic mechanism that involves sequential addition of O-methyl groups to residues of the pre-formed D-glucan, in the reducing-to-nonreducing residue direction.
通过用L-[³H-Me]甲硫氨酸培养耻垢分枝杆菌不同时间，研究了O-甲基基团酶促掺入耻垢分枝杆菌含O-甲基-D-葡萄糖的多糖（MGP）中的顺序，即3MG(J)----G(I)----G(H) ----G(G)----6MG(F)----(GMG)9(E)----[G(L)----G(D)]----G(C) ----[G(K)----G(B)]----G(A)----Ga，其中G为D-葡萄糖，3MG为3-O-甲基-D-葡萄糖，6MG为6-O-甲基-D-葡萄糖，Ga为D-甘油酸。然后从细胞中提取MGP，并测定残基D、(E + F)平均值和J，或D、E平均值、F和J的相对放射性。这些残基的氚标记在还原端到非还原端残基方向上增加，随着孵育时间的增加，梯度的陡度变得更平缓。结果与一种生物合成机制一致，该机制涉及在还原端到非还原端残基方向上，将O-甲基基团依次添加到预先形成的D-葡聚糖的残基上。
