ISOFORMS OF AN N-ACETYL-BETA-D-GLUCOSAMINIDASE FROM THE ANTARCTIC KRILL, EUPHAUSIA-SUPERBA - PURIFICATION AND ANTIBODY-PRODUCTION

Two forms of the chitinolytic enzyme N-acetyl-beta-D-glucosaminidase ( NAGase, EC 3.2.1.52) have been isolated from the Antarctic krill, Euph ausia superba, in order to study their potential role in temperature a daptation processes. A chromatographic protocol was developed that all owed complete separation of the two enzyme forms, named NAGase B and N AGase C. The latter was purified to homogeneity with 600-fold enrichme nt and a yield of 17%. The molecular mass was 150 kDa. NAGase B showed characteristics of a glycoprotein due to affinity towards concanavali n A sepharose, while NAGase C did not. Highly specific polyclonal anti bodies to NAGase C [anti-(E. superba-NAGase C)-IgG] showed only neglig ible cross-reactivity with NAGase B isoforms. A comparison with the No rthern krill, Meganyctiphanes norvegica,revealed a corresponding chrom atographic pattern with two main activity peaks, for differentiation n amed NAGase II and NAGase III. Application of the antibody on M. norve gica revealed a high specificity toward NAGase III and a low cross-rea ctivity with NAGase II. First indication is given that the two forms a re no isoenzymes in a strict sense but instead may have different func tions in the metabolism of krill. (C) 1998 Elsevier Science Inc. All r ights reserved.