The enzymic synthesis, by transglucosylation of a homologous series of glycosidically substituted malto-oligosaccharides, and their use as amylase substrates

Abstract

(1 → 4)-α- d-Glucan 4-glucosyltransferase (EC2.4.1.19) of klebsiella pneumoniae transforms maltose (G2) into d-glucose (G1) and a mixture of malto-oligosaccharides (G 2—G 9), and maltotriose (G3) into G l—G ll in addition to cyclo-hexa-, -hepta-, and -octa-amyloses (cG 6—8). It produces a similar mixture, but with higher amounts of G 2—G 11, by transfer from cyclohexaamylose to G 1. By using p-nitrophenyl α- and β- d-glucosides, 4 methylumbelliferyl α- d-glucoside, and strophanthyl α- d-glucoside as acceptors and cyclohexaamylose as donor, a homologous series of substituted malto-oligosaccharides having chain lengths of up to 12 d-glucose residues was produced. High-pressure liquid chromatography on Bio-Gel P 2 permitted separation of these products of transferase activity on analytical and preparative scales. By the same technique, the nitration product of phenyl hepta- O-acetyl-α-maltoside, after deacetylation, was separated into about equal amounts of the o- and p-isomers. The synthetic p-nitrophenyl α-maltoside ( pNPG 2) was used to identify the first member of the series of biochemical transfer-products. p-Nitrophenyl maltotrioside ( pNPG 3) and maltotetraoside ( pNPG 4) were shown to be the higher homologues. They are very good substrates for human and pig-pancreatic alpha amylase. This substrate behavior may be measured conveniently in the case ofpNPG3 by the rapid liberation of nitrophenolate; the enzyme used pNPG 4 only on addition of α- d-glucosidase. Human-parotis amylase of equal starch-splitting activity as the pancreatic enzyme acts upon pNPG 3 and pNPG 4 but about 100 times more slowly.