| First Author | Nichols BL | Year | 1998 |
| Journal | J Biol Chem | Volume | 273 |
| Issue | 5 | Pages | 3076-81 |
| PubMed ID | 9446624 | Mgi Jnum | J:45511 |
| Mgi Id | MGI:1195543 | Doi | 10.1074/jbc.273.5.3076 |
| Citation | Nichols BL, et al. (1998) Human small intestinal maltase-glucoamylase cDNA cloning. Homology to sucrase-isomaltase. J Biol Chem 273(5):3076-81 |
| abstractText | It has been hypothesized that human mucosal glucoamylase (EC 3.2.1. 20 and 3.2.1.3) 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. |
