ALPHA-GLUCOSIDASE FROM THE HEPATOPANCREAS OF THE SHRIMP, PENAEUS-VANNAMEI (CRUSTACEA-DECAPODA)

Penaeus vannamei is an omnivorous species, and it can be assumed that a high level of carbohydrates is necessary for growth. Alpha-glucosida ses are important enzymes necessary for the ultimate liberation of glu cose residues from various carbohydrates. Using acarbose affinity chro matography, a glycosylated alpha-glucosidase with a molecular mass of approximately 105 kDa was isolated for the first time from the hepatop ancreas of the shrimp. Exhibiting an optimal catalytic activity in the temperature range from 40 degrees C to 50 degrees C at pH 6, the puri fied enzyme hydrolyses alpha 1-4 bonds and liberates glucose from diff erent oligo and polysaccharides. By contrast to other known glucosidas es, no alpha 1-6 glucose link with hydrolysis has been observed. This could explain the different rates of growth in shrimp aquaculture with starches from various origins. The amino-acid composition, together w ith the partial sequence of a hydrolytic peptide, shows a high degree of similarity to the alpha-glucosidases reported for various organisms including yeast and fungi and may help determine the phylogeny of the family. (C) 1998 Wiley-Liss, Inc.