Two-Dimensional Electrophoretic Study of the Water-Soluble Protein Fraction in White Muscle of Gadoid Fish Species

Abstract

Eight gadoid fishesfive hakes (Merluccius spp.), cod (Gadus morhua), pollack (Pollachius pollachius), and blue whiting (Micromesistius poutassou)were characterized in their water-soluble protein profiles by two-dimensional (2D) electrophoresis both by nondenaturing isoelectric focusing (IEF) in the 4−6.5 pH range and gradient SDS−PAGE in the 12−14% range. Species-specific parvalbumin patterns (MW < 13 kDa, pI < 4.6) were observed in most of the species. 2D analysis of mixed extracts revealed that M. merluccius had one parvalbumin (10.4 kDa, pI 3.9) in common with M. australis and M. hubbsi, and two parvalbumins (10.3 kDa, pI 4.1; 10.4 kDa, pI 3.9) in common with M. capensis, respectively. 2D electrophoresis allowed detailed characterization of both the isoelectric points and molecular weights of the major water-soluble proteins and proved to be a valuable tool for the differential characterization among closely related Merluccius spp. Keywords: Identification; species; 2D electrophoresis; isoelectric focusing; fish; Merluccius spp.; gadoids