Enzymatic catalysts in organic synthesis

ELAM-1--dependent cell adhesion to vascular endothelium determined by a transfected human fucosyltransferase cDNA

Adhesion of circulating leukocytes to the vascular endothelium during inflammation is mediated in part by their interaction with the endothelial-leukocyte adhesion molecule ELAM-1. ELAM-1, a member of the LEC-CAM family of cell adhesion molecules, expresses an N-terminal carbohydrate recognition domain (CRD) homologous to various calcium-dependent mammalian lectins. However, the contribution of the CRD to cell adhesion and its carbohydrate binding specificity have not been elucidated. This study demonstrates that transfection of a human fucosyltransferase cDNA into nonmyeloid cell lines confers ELAM-1--dependent endothelial adhesion. Binding activity correlates with de novo cell surface expression of the sialylated Lewis x tetrasaccharide, whose biosynthesis is determined by the transfected fucosyltransferase cDNA. We propose that specific alpha(1,3)fucosyltransferases regulate cell adhesion to ELAM-1 by modulating cell surface expression of one or more alpha(2,3)sialylated, alpha(1,3)fucosylated lactosaminoglycans represented by the sialyl Lewis x carbohydrate determinant.

The unique stability of Vibrio proteolyticus neutral protease under alkaline conditions affords a selective step for purification and use in amino acid-coupling reactions

A procedure is described for the purification of a neutral protease from fermentation broths of Vibrio proteolyticus. The key feature of the purification scheme is the selective, irreversible inactivation of a contaminating exoenzyme, aminopeptidase, by alkali treatment, rather than removal of this enzyme by conventional chromatographic methods. Fermentation broths or concentrates were brought to pH 11.5 to 11.7 by Na2CO3-NaOH addition and incubated at 25 degrees C until aminopeptidase activity was diminished. The alkali treatment resulted in greater than 99% reduction of aminopeptidase activity with minimal loss of neutral protease activity. The neutral protease could be further purified to apparent homogeneity by QA-52 cellulose chromatography. The alkali treatment of fermentation concentrates was also useful for preparation of V. proteolyticus neutral protease to effect the coupling of N-protected aspartic acid and phenylalanine methyl ester for the production of N-aspartylphenylalanine methyl ester, a precursor for the sweetener aspartame.