Biochimica et Biophysica Acta, 342 (1974) 209--212 (~) Elsevier Scientific Publishing Company, Amsterdam -- Printed in The Netherlands BBA Report BBA 31173 EVIDENCE THAT FICIN IS A GLYCOPROTEIN BERNARD FRIEDENSON and IRVIN E. LIENER Department of Biochemistry, College of Biological Sciences, University of Minnesota, St. Paul, Minnesota 55101 (U.S.A.) (Received January 28th, 1974) Summary A glycopeptide was isolated from a peptic digest of ficin by successive chromatography on cationic and anionic exchange resins followed by gel filtration. The polypeptide portion of this glycopeptide consisted of 9 amino acids to which was attached a carbohydrate moiety comprised of glucosamine, mannose, galactose, fucose and xylose in molar ratios of 5: 2:1 : 1 : 1, respectively. This glycopeptide appears to resemble in many respects a similar glycopeptide isolated from bromelain (Kito, K. and Murachi, T. (1969) J. Chromatogr. 44, 205--207; Scocca, J. and Lee, Y.C. {1969) J. Biol. Chem. 244, 4852- 4863). The plant thiol proteases (papain, ficin, and bromelain) have very similar physical and chemical properties and probably operate via the same catalytic mechanism [1 ], Despite this similarity, there appear to be marked differences with respect to carbohydrate content. Although papain is devoid of sugar residues, bromelain has been reported to contain 1.5% [2] to 2% [3] carbohydrate, and the oligosaccharide moiety has been characterized by Murachi and coworkers [4] and Scocca and Lee [5]. The situation with respect to ficin is much less certain. Englund et al. [6] concluded on the basis of their studies that ficin was probably not a glycoprotein, whereas Jones and Glazer [7] reported the presence of about 1% carbohydrate which was not further characterized. This communication describes the isolation and partial charac- terization of a glycopeptide derived from ficin, thus providing unequivocal evidence that this enzyme is a glycoprotein. The ficin used in this study was purified according to Friedenson and Liener [8] and consists of three closely related active components. To 100 mg