UDP-N-acetyl-D-galactosamine as a donor substrate for the glycosyltransferase encoded by the B gene at the human blood group ABO locus

The properties of the enzyme in the serum of blood group B individuals that catalyses the transfer of small amounts of N-acetyl-D-galactosamine to H-active precursor structures were compared with those of the blood group B gene-associated alpha-(1----3)-D-galactosyltransferase and with the blood group A gene-associated alpha-(1----3)-N-acetyl-D-galactosaminyltransferases in the serum of blood group A1 and A2 individuals. The biosynthetic products formed by the enzyme in B serum were identical with the A-active structures synthesised by the A1 and A2 gene-associated alpha-(1----3)-N-acetyl-D-galactosaminyltransferases but the enzyme differed from the A1 and A2 transferases in its apparent Km for UDP-N-acetyl-D-galactosamine, its heat susceptibility, its failure to bind to Sepharose 4B, and its adsorption to H-active sites on group O red cell ghosts under conditions which bind the B transferase but fail to adsorb the A1 and A2 transferases. The correlation between the levels of alpha-(1----3)-D-galactosyltransferase and alpha-(1----3)-N-acetyl-D-galactosaminyltransferase activities in all the group B serum samples tested, the maintenance of the same ratio of activities after successive cycles of binding to group O red cell ghosts, the retention of the ability to convert blood group O to A-active cells after treatment of the serum with Sepharose 4B, and the failure to detect any comparable activity in group O serum samples tested under the same conditions indicated that the enzyme in group B serum that utilises UDP-N-acetyl-D-galactosamine to make blood group A-active structures is the B gene-associated alpha-(1----3)-D-galactosyltransferase.     

Differential concanavalin A binding of cystic fibrosis and normal liver alpha-L-fucosidase.

A novel technique has been employed to demonstrate that α-L-fucosidase purified from cystic fibrosis and control livers exhibits differential binding to the lectin Concanavalin A. The concentration of α-CH₃-mannoside necessary to prevent 50% binding of α-L-fucosidase to Concanavalin A is considerably lower for the cystic fibrosis enzyme (13.5 vs. 33.3 mM). Comparable results were found when binding studies were done on crude supernatant α-L-fucosidase from 8 cystic fibrosis and 8 control livers (5.6 ± 0.4 mM and 13.2 ± 3.4 mM, respectively), without any overlap of values between the cystic fibrosis and control livers. These results suggest that comparative lectin binding studies on cystic fibrosis and normal glycoproteins from readily available tissues might result in an assay for detecting the cystic fibrosis genotype.     

Stereoselective formation of bis(alpha-aminoacyl) esters of 5'-AMP suggests a primitive peptide synthesizing system with a preference for L-amino acids

In the biosynthesis of proteins, each amino acid passes from the aminoacyl adenylate to become an amino acid ester and finally a 2' (3') peptidyl ester of the AMP residue at the end of a tRNA. Consequently, the chemistry of protein synthesis is the chemistry of aminoacyl and peptidyl AMP. Our data has revealed properties of 5'-AMP and its esters which should allow the preferential catalytic synthesis of L-amino acid peptides via a bis(2', 3'-aminoacyl) ester intermediate. Results in this paper concern one step in the proposed process and show that preexisting Ac-L-Phe monoester reacts about 2.5-times faster to form diester than preexisting Ac-D-Phe monoester.     

The effect of NaCl intake on 9-ketoprostaglandin reductase activity in the rabbit kidney

Renal 9-ketoprostaglandin reductase activity from rabbits fed 0.3 g or 2.5 g NaCl per 100 g chow was measured in both centrifuged homogenates and in purified enzyme fractions. There was no salt related increase in 9-ketoprostaglandin reductase activity. PGA1-glutathione, 9, 10-phenanthrenequinone, and 4-nitrobenzaldehyde were better substrates for the purified 9-ketoprostaglandin reductases than was PGE2. Several carbonyl reductases were isolated which used PGA1-glutathione, 9, 10-phenanthrenequinone, and 4-nitrobenzaldehyde, but not PGE2, as substrates. Although PGA1-glutathione was a more faithful indicator of PGE2-related 9-ketoprostaglandin reductase activity than either 9, 10-phenanthrenequione or 4-nitrobenzaldehyde, it did not always provide an accurate estimate of that activity.     

Purification to homogeneity and partial characterization of a 56,000-dalton protein phosphatase from rabbit reticulocytes

A 56,000-Da peptide with inherent protein phosphatase activity was isolated from the postribosomal supernatant fraction of rabbit reticulocytes. The peptide appears to form complexes with other proteins that are present in crude fractions. It exhibits atypical retention on steric exclusion columns during high performance liquid chromatography, an unusual characteristic that facilitated its isolation. The protein phosphatase activity of the 56,000-Da peptide is dependent on Mn2+ ions, but is not activated by either the FA, ATP/Mg2+ protein phosphatase activator system or by proteolysis. The protein phosphatase activity of the peptide is increased 3-fold or more by the antigen peptides described in the accompanying paper (Fullilove, S., Wollny, E., Stearns, G., Chen, S.C., Kramer, G., and Hardesty, B. (1984) J. Biol. Chem. 259, 2493-2500).