Protein Structures of Common Bean (Phaseolus vulgaris) α-Amylase Inhibitors

Abstract

Two nucleotide sequences for genes that encode alpha-amylase inhibitor 4 (alphaAI-4) from white kidney bean (WKB) cv. 858, designated gene alphaAI-4 (Accession No. ), and alpha-amylase inhibitor 5 (alphaAI-5) from black bean (BB), designated gene alphaAI-5 (Accession No. ), were determined. Genes alphaAI-4 and alphaAI-5 encode 244 amino acid prepro-alphaAI-4 and prepro-alphaAI-5 polypeptides that are 93 and 95% identical with alpha-amylase inhibitor l (alphaAI-l; Hoffman, L. M.; Ma, Y.; Barker, R. F. Nucleic Acids Res. 1982, 10, 7819-7828), 40 and 43% identical with red kidney bean lectin, and 52 and 55% identical with arcelin l of wild-type bean. The high degree of sequence similarity indicates the evolutionary relationship among these genes. PCR analysis of genomic DNA purified from six genotypes of Phaseolus vulgaris showed very similar band patterns in 2% agarose gel, another indication of the conserved size homology among these genes. Proteolytic processing sites were located between Asn77 and Ser78 for pro-alphaAI-4 and pro-alphaAI-5. A bend next to Asn77 in three-dimensional model structures of alphaAI-4 and alphaAI-5 proinhibitors indicates that the proteolytic cleavage is necessary to remove the conformational constraint for activation to the mature protein. Mature WKB alphaAI-4 was composed of four subunits (2alpha2beta) and had a molecular weight of 50000 determined by multiangle laser light scattering and 56714 determined by laser-assisted time-of-flight mass spectrometry.

Polysaccharide utilisation loci of Bacteroidetes from two contrasting open ocean sites in the North Atlantic

“…In contrast, ORF VISS18_034_02 belongs to the GH13_20 subfamily that includes cyclomaltodextrinase, neopullulanase and maltogenic amylase. In comparison to classical alphaamylases, these enzymes, and also ORF VISS18_034_02, feature an extra domain that participates in dimer formation (Lee et al, 2002;Stam et al, 2006). Cyclomaltodextrinases effectively hydrolyze cyclomaltodextrin, a circular sugar derived from starch degradation, whereas the degradation of starch and pullulan is less effective (Lee et al, 2002).…”

“…In comparison to classical alphaamylases, these enzymes, and also ORF VISS18_034_02, feature an extra domain that participates in dimer formation (Lee et al, 2002;Stam et al, 2006). Cyclomaltodextrinases effectively hydrolyze cyclomaltodextrin, a circular sugar derived from starch degradation, whereas the degradation of starch and pullulan is less effective (Lee et al, 2002). The PUL also contains a putative GH31 family alphaglucosidase (ORF VISS18_034_01), which hydrolyzes the oligosaccharides released by alpha-amylases.…”

Potential efficacy of preparations derived from Phaseolus vulgaris in the control of appetite, energy intake, and carbohydrate metabolism

“…The latter constituents belong to the class of lectins, highly represented in different cereals and pulses, including P. vulgaris . These lectins – together with arcelins, another type of lectins abundant in P. vulgaris – are homologous proteins displaying high degrees (40% to 95%) of aminoacid sequence similarity 16–19…”

Reducing Effect of a Combination of Phaseolus vulgaris and Cynara scolymus Extracts on Food Intake and Glycemia in Rats

“…Two possible mechanisms of action have been proposed to explain the lowering effect of P. vulgaris extracts and derivatives on food intake and glycemia: (a) inhibition of pancreatic α‐amylase, resulting in deceleration of carbohydrate metabolism and absorption, decrease in glycemia, and production of feelings of satiety (e.g. Lee et al ., ; Santimone et al ., ; Tormo et al ., ); (b) reduction—induced by phytohemoagglutinins, a major ingredient of P. vulgaris —of appetite and gastrointestinal transit, likely via alterations in the release of cholecystokinin and glucagon‐like peptides (both known to be involved in digestive processes and central control of appetite) (e.g. Donatucci et al ., ; Herzig et al ., ; Pusztai et al ., ).…”