Barley alpha-amylase isozymes AMY1 and AMY2 contain three structural domains: a catalytic (beta/alpha)8-barrel (domain A) with a protruding loop (domain B; residues 89-152) that binds Ca2+, and a small C-terminal domain. Different parts of domain B secure isozyme specific properties as identified for three AMY1-AMY2 hybrids, obtained by homeologous recombination in yeast, with crossing-over at residues 112, 116, and 144. The AMY1 regions Val90-Thr112 and Ala145-Leu161 thus confer high affinities for the substrates alpha-D-maltoheptaoside and amylose, respectively. Leu117-Phe144, and to a lesser degree Ala145-Leu161, are critical for the stability at low pH characteristic of AMY1 and for the sensitivity to barley alpha-amylase/subtilisin inhibitor specific to AMY2.
|Journal||F E B S Letters|
|Publication status||Published - 1995|
Juge, N., Rodenburg, K. W., Guo, X-J., Chaix, J-C., & Svensson, B. (1995). Isozyme hybrids within the protruding third loop domain of the barley alpha-amylase (beta/alpha)8-barrel. Implication for BASI sensitivity and substrate affinity. F E B S Letters, 363, 299-303. http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=Abstract&list_uids=7737421&query_hl=40&itool=pubmed_docsum