Smith degradation units

In a similar series of experiments, Unrau and Choy59 found that the structure of Caesalpinia pulcherima galactomannan differs from the normal type of structure, but to a much lesser extent —4% of the D-mannose units in the main chain are /3-D-(l — 3)-linked, and 2% are ( 1 — 2)-linked. Smith degradation again indicated that isolated and consecutive /8-D-(l — 3)-linkages were present in the main chain. 

An apparently similar type of mannan is formed exocellularly by a certain Rhodotorula species. Rhodotorula glutinis mannan has a specific rotation of —78°, and consists of a linear chain of at least 90 units, which is overoxidized somewhat with periodate, consuming 0.61 mole of oxidant with formation of 0.07 mole of acid per mole of mannose residue after two days. Partial hydrolysis gives 4-0-)3-D-mannopyranosyl-D-mannose and 0-j8-D-mannopyranosyl-(1 3)-0-/8-D-mannopyranosyl-(1 4)-D-mannose, but a)8-D-(l- 4)-linked manno-triose is not detectable. Since 2-0-j8-D-mannopyranosyl-D-erythritol is obtained from the mannan by a Smith degradation, an alternating ar-... 

T. Krusius and J. Fiime, Use of the Smith degradation in the study of the branching pattern in the complex-type carbohydrate units of glycoproteins, Carbohydr. Res., 90 (1981) 203-214. 

D-mannose. Smith degradation destroyed the side-chain residues and left an a-(1 3)-linked mannan backbone, [a]j)+43°. Partial acid hydrolysis liberated g-xylose and the disaccharide 4-0 -a-L-arabinopyranosyl-D-xylose. These results, together with those of methylation analyses, suggested a branched structure wherein some of the (1 3)-linked mannosyl backbone residues are substituted with D-xylopyranosyl, g-mannopyranosyl and 4-0-a-L-arabinopyra-nosyl-g-xylopyranosyl units. 

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