Human small intestinal maltase-glucoamylase cDNA cloning. Homology to sucrase-isomaltase

J Biol Chem. 1998 Jan 30;273(5):3076-81. doi: 10.1074/jbc.273.5.3076.


It has been hypothesized that human mucosal glucoamylase (EC 3.2.1. 20 and activity serves as an alternate pathway for starch digestion when luminal alpha-amylase activity is reduced because of immaturity or malnutrition and that maltase-glucoamylase plays a unique role in the digestion of malted dietary oligosaccharides used in food manufacturing. As a first step toward the testing of this hypothesis, we have cloned human small intestinal maltase-glucoamylase cDNA to permit study of the individual catalytic and binding sites for maltose and starch enzyme hydrolase activities in subsequent expression experiments. Human maltase-glucoamylase was purified by immunoisolation and partially sequenced. Maltase-glucoamylase cDNA was amplified from human intestinal RNA using degenerate and gene-specific primers with the reverse transcription-polymerase chain reaction. The 6,513-base pair cDNA contains an open reading frame that encodes a 1,857-amino acid protein (molecular mass 209,702 Da). Maltase-glucoamylase has two catalytic sites identical to those of sucrase-isomaltase, but the proteins are only 59% homologous. Both are members of glycosyl hydrolase family 31, which has a variety of substrate specificities. Our findings suggest that divergences in the carbohydrate binding sequences must determine the substrate specificities for the four different enzyme activities that share a conserved catalytic site.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Binding Sites
  • Cattle
  • Cloning, Molecular*
  • Consensus Sequence
  • DNA, Complementary
  • Escherichia coli / genetics
  • Haplorhini
  • Humans
  • Intestine, Small / enzymology*
  • Mice
  • Molecular Sequence Data
  • Rabbits
  • Rats
  • Recombinant Proteins / biosynthesis
  • Species Specificity
  • Substrate Specificity
  • Tissue Distribution
  • alpha-Glucosidases / genetics*


  • DNA, Complementary
  • Recombinant Proteins
  • alpha-Glucosidases

Associated data

  • GENBANK/AF016833