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Appl. Environ. Microbiol., Aug 1995, 2885-2890, Vol 61, No. 8
T Semimaru, M Goto, K Furukawa and S Hayashida
Glucoamylase I (GAI) from Aspergillus awamori var. kawachi hydrolyzes raw
starch efficiently and is composed of three functional domains: the
amino-terminal catalytic GAI' domain (A-1 to V-469), the threonine- and
serine-rich O-glycosylated Gp-I domain (A-470 to V-514), and the
carboxy-terminal raw starch-binding Cp domain (A-515 to R-615). In order to
investigate the role of the Gp-I domain, an additional repeat of Gp-I and
internal deletions of the entire Gp-I sequence or parts of the Gp-I
sequence were introduced within Gp-I. All mutant genes as well as the
wild-type gene were inserted into a yeast-secretion vector, YEUp3H alpha,
and expressed in Saccharomyces cerevisiae. Wild-type GAI expressed in yeast
cells (GAY), GAGpI, having an extra Gp-I, and GA delta 470-493, lacking the
A-470-to-T-493 sequences of Gp-I, were successfully secreted into the
culture medium. On the other hand, GA delta 470-507, lacking A-470 to
S-507, and GA delta GpI, lacking the entire Gp-I (A-470-to-V-514) sequence,
failed to be secreted and remained in the yeast cells. The carbohydrate
content of GAGpI was 1.2 times higher than that of GAY and 2.4 times higher
than that of the original GAI. The raw starch digestibility of GAGpI was
almost the same as that of GAY but was 1.5 times faster than that of
GAI.(ABSTRACT TRUNCATED AT 250 WORDS)
Copyright © 1995, American Society for Microbiology
Functional analysis of the threonine- and serine-rich Gp-I domain of glucoamylase I from Aspergillus awamori var. kawachi
Department of Agricultural Chemistry, Kyushu University, Fukuoka, Japan.
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