Panayotatos N, Villemez C L
Biochem J. 1973 Jun;133(2):263-71. doi: 10.1042/bj1330263.
With a particulate enzyme preparation from Phaseolus aureus hypocotyls, UDP-alpha-d-[U-(14)C]galactose served as a precursor for a number of products. One of these products was characterized as a beta-(1-->4)-linked galactan. The ADP-, GDP-, TDP- and CDP- derivatives of alpha-d-galactose did not serve as biosynthetic precursors for any products insoluble in 70% ethanol, nor as substrates for a sugar nucleotide 4-epimerase which is present in the particulate enzyme preparation. The (14)C-labelled beta-(1-->4)-galactan is alkali-insoluble and was characterized by analysis of partial acetolysis products. The labelling pattern of the [(14)C]oligosaccharides derived from acetolysis indicates that (1) only slightly more than two [(14)C]galactose moieties are added to the growing polysaccharide chain on average, and (2) these additions take place at the reducing end of the polysaccharide chain. The radioactive beta-(1-->4)-linked galactan chain represented 8.5% of the radioactivity initially added, and 20% of the water- and butanol-insoluble products derived from UDP-alpha-d-[(14)C]galactose. Total hydrolysis of the alkali-insoluble fraction of Phaseolus aureus hypocotyl yielded d-glucose and d-mannose in a 5:1 ratio but no detectable quantities of d-galactose. A trace quantity of a radioactive disaccharide, identified as (1-->3)-linked galactobiose, was isolated from the partial acetolysate of the alkali-insoluble [(14)C]polysaccharide material. Also isolated from this partial acetolysate was a C-1 derivative of [(14)C]galactose, which could not be identified. An alkali-soluble galactose-containing polysaccharide was also synthesized in this enzymic reaction, and represented 20% of the water- and butanol-insoluble products derived from UDP-alpha-d-[(14)C]galactose. The spectrum of radioactive oligosaccharides produced by partial acetolysis of this alkali-soluble polysaccharide material was different from that obtained from the alkali-insoluble polysaccharide, indicating a different structure.
使用来自金甲豆下胚轴的颗粒状酶制剂，UDP-α-D-[U-(14)C]半乳糖可作为多种产物的前体。其中一种产物被鉴定为β-(1→4)连接的半乳聚糖。α-D-半乳糖的ADP-、GDP-、TDP-和CDP-衍生物既不作为任何不溶于70%乙醇的产物的生物合成前体，也不作为颗粒状酶制剂中存在的糖核苷酸4-表异构酶的底物。(14)C标记的β-(1→4)-半乳聚糖不溶于碱，通过对部分乙酰解产物的分析对其进行了表征。来自乙酰解的[(14)C]寡糖的标记模式表明：(1)平均而言，在生长的多糖链上仅添加略多于两个[(14)C]半乳糖部分；(2)这些添加发生在多糖链的还原端。放射性β-(1→4)连接的半乳聚糖链占最初添加放射性的8.5%，占UDP-α-D-[(14)C]半乳糖衍生的水和丁醇不溶性产物的20%。金甲豆下胚轴碱不溶性部分的完全水解产生了比例为5:1的D-葡萄糖和D-甘露糖，但未检测到D-半乳糖。从碱不溶性[(14)C]多糖材料的部分乙酰解产物中分离出微量放射性二糖，鉴定为(1→3)连接的半乳糖二糖。还从该部分乙酰解产物中分离出一种无法鉴定的[(14)C]半乳糖的C-1衍生物。在该酶促反应中还合成了一种碱溶性含半乳糖的多糖，占UDP-α-D-[(14)C]半乳糖衍生的水和丁醇不溶性产物的20%。该碱溶性多糖材料部分乙酰解产生的放射性寡糖谱与碱不溶性多糖的不同，表明结构不同。
