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

(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 (G₂—G₉), 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 G₂—G₁₁, by transfer from cyclohexaamylose to G₁. 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 P₂ 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 (_pNPG₂) was used to identify the first member of the series of biochemical transfer-products. p-Nitrophenyl maltotrioside (_pNPG₃) and maltotetraoside (_pNPG₄) 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 _pNPG₄ only on addition of α-d-glucosidase. Human-parotis amylase of equal starch-splitting activity as the pancreatic enzyme acts upon _pNPG₃ and _pNPG₄ but about 100 times more slowly.