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Biomedical subjects

Y Bai

Publications and source records attributed to Y Bai.

216 records · Page 12Linked to original sources
PubMed1982

Monoclonal anti-type 2 H: an antibody detecting a precursor of the A and B blood group antigens.

A monoclonal antibody was produced which binds specifically to Type 2 H antigen of the ABO blood group system. The antibody, H11, is an IgM molecule which reacts by direct agglutination of red cells with the same pattern as other anti H reagents such as Ulex europaeus lectin. The specificity was determined by inhibition and adsorption with chemically defined oligosaccharides. H11 also reacted with poly (glycosyl) ceramide purified from group 0 red cells and glycoprotein H purified from human stomach mucosa and meconium. H11 differs from Ulex lectin, however, in that it was not inhibited by saliva from ABH secretor individuals or by glycoprotein H purified from human ovarian cysts or submaxillary glands.

ABO Blood-Group System↗
PubMed1975

Evidence for an essential histidine in carboxypeptidase Y. Reaction with the chloromethyl ketone derivative of benzyloxycarbonyl-L-phenylalanine.

The possible role of histidine residues in the catalytic function of carboxypeptidase Y from bakers' yeast has been investigated using site-specific reagents. Among the reagents tested, benzyloxy-L-phenylalanylchloromethane (Z-PheCH2Cl) was the most powerful inhibitor of the enzyme. It irreversibly inactivated both the peptidase and esterase activities with an apparent second order rate constant of 3.8 M-minus 1 S-minus 1; the D isomer caused essentially no effect on either activity. Inhibition by L-Z-PheCH2Cl, the reaction retarded by certain competitive inhibitors of the enzyme. Using radioactive L-Z-PheCH2Cl, the reaction with the enzyme was shown to be essentially stoichiometric. Diisopropylphosphorofluoridate (iPr2PF)-inactivated enzyme failed to react with Z-PheCH2Cl, and conversely, the Z-PheCH2Cl-inhibited enzyme failed to react with radioactive iPr2PF. Amino acid analyses of the Z-PheCH2Cl-inactivated enzyme revealed the loss of essentially 1 residue, with a concomitant yield of a 0.62 residue of N-t-carboxymethylhistidine. Since carboxypeptidase Y has a reactive serine at its active center, we concluded from these results that the mechanism involves a charge-relay system in the hydrolysis of peptide and ester substrates, as in chymotrypsin. An -SH group of carboxypeptidase Y was not affected during the reaction with L-Z-PheCH2Cl. The generic name "serine carboxypeptidase" has been proposed for carboxypeptidase Y and for the iPr2PF-sensitive carboxypeptidases from plants, molds, and animal tissues, in order to distinguish them from "metal carboxypeptidase" to which carboxypeptidase A (EC 3.4.12.2) and B (EC 3.4.12.3) belong.

Amino Acids↗
PubMed1975

Kinetic studies of carboxypeptidase Y. I. Kinetic parameters for the hydrolysis of synthetic substrates.

Kinetic parameters for carboxypeptidase Y [EC 3.4.12.1], characterized as a nonspecific enzyme, are given for the hydrolysis of a series of acylated peptides, acylated amino acid esters, and amides. We confirmed that the enzyme released COOH-terminal proline and beta-alanine at an appreciable rate, as well as neutral amino acids with aromatic and aliphatic side chains at a very high speed. The rates of hydrolysis of ester and amide substrates were compatible with those produced by chymotrypsin [EC 3.4.21.1]. Stereospecificity was also demonstrated by the failure to hydrolyze peptide, ester, amide, and anilide substrates containing a D-amino acid. The effects of pH, solvents, and salt concentrations on the kinetic parameters of hydrolysis of peptide and ester substrates are also described.

Anilides↗
PubMed1975

Kinetic studies of carboxypeptidase Y. II. Effects of substrate and product analogs on peptidase and esterase activities.

Reversible inhibition of the peptidase and esterase activities of CPase Y [EC 3.4.12.1] was investigated with substrate and product analogs known to be inhibitors or effectors of pancreatic carboxypeptidases A or B [EC 3.4.12.2 or 3]. L-Amino acids and NH2-blocked L-Amino acids showed competitive-type inhibition, whereas their D-enantiomers caused less inhibition than the L-enantiomers, and showed non-competitive or mixed-type inhibition. Some phenylalanine analogs, e.g. beta-phenylpropionic acid and t-cinnamic acid, were also reversible inhibitors of CPase Y. The type of these inhibitors and their K1 values were generally parallel for both the peptidase and esterase activities.

Amino Acids↗
PubMed1975

Kinetic studies of carboxypeptidase Y. III. Action on ester, amide, and anilide substrates and the effects of some environmental factors.

Kinetic parameters of carboxypeptidase Y are given for the hydrolyses of ester, amide, and anilide substrates. The kcat/Km values were compatible with those of chymotrypsin [EC 3.4.21.1] with a few exceptions. One ionizable group with a pK of around 5.8 was suggested to be involved in the free enzyme in hydrolyzing all the substrates, including peptide substrates. In addition, hydroxylaminolysis and the kinetic isotope effects of deuterium oxide indicated, with some reservations, a reaction mechanism which proceeds via the formation of an acyl intermediate.

Amides↗
PubMed1975

Further confirmation of carboxypeptidase Y as a metal-free enzyme having a reactive serine residue.

The metal content of carboxypeptidase Y was analyzed by the atomic absorption method. After exhaustive dialysis against an EDTA solution, the enzyme showed no loss of activity nor any significant content of metals (Zh,Mg,Ca,Cu,Mn,Ni,Fe, and Co). The activity was, however, rather sensitive to preincubation with various metals. The reactivity of a serine residue of the enzyme was also reevaluated. Diisopropyl fluorophosphate (DFP) and phenylmethanesulfonyl fluoride (PMSF) stoichiometrically and irreversively inhibited the enzyme. The rate of inactivation with DFP was much faster than that for typsin [EC 3.4.21.4] and chymotrypsin [EC 3.4.21.1.], while the rate with PMSF was one-fifteenth of that for chymotrypsin. The pH-dependence of the inactivation by DFP was similar to that of the enzymatic hydrolysis of acetylphenylalanine ethyl ester. The present results indicate that carboxypeptidase Y is free of metals and has a serine residue with a vital role in the catalytic process, though the functional role of this SH group remains to be clarified.

Apoenzymes↗
PubMedDate not supplied

Effect of processing on the recovery of recombinant beta-glucuronidase (rGUS) from transgenic canola.

This study addresses the processing of transgenic canola seed for production of recombinant proteins by using beta-glucuronidase (rGUS) as a model protein. The major processing steps that were investigated included dry and wet grinding of the seed, solvent extraction of canola oil, and protein extraction. rGUS in canola seed was stable for at least 2 weeks of incubation at 38 degrees C and for more than 5 months at 10 degrees C. At 70 degrees C, the residual activity changed inversely to the initial moisture content of the seed. The comparison of wet and dry processing revealed no significant differences in protein recovery. rGUS was stable during the defatting of transgenic canola flakes with hexane at 66 degrees C, whereas 2-propanol extraction at the same temperature reduced the extractable enzyme activity by almost 50%. The particle size of the ground seed was important for the extraction efficiency. A faster extraction and greater protein yield was achieved by extracting particles with an average diameter equal to or smaller than 255 microm. More than 80% rGUS was extracted in one stage with sodium phosphate buffer of pH 7.5.

Blotting, Western↗
PubMedDate not supplied

Histological study of tibial dyschondroplasia-like lesion from light-type chicks fed cysteine-supplemented diets.

Tibial dyschondroplasia (TD)-like lesions were induced in New Hampshire x Single-Comb White Leghorn cross chicks (NH x SCWL) by feeding excess levels of cysteine. The chicks fed a corn/soybean-meal-based diet had no spontaneous TD. The chicks fed the basal diet supplemented with 1.5% or 3.0% cysteine showed more than 50% TD-like lesions at 10 days of age; in another experiment, 1.6% cysteine induced TD (15%) at 3 weeks of age. A low incidence of rachitic-like lesions was found in Expt. 2 but was not associated with the dietary treatments. The TD-like lesion had a normal upper growth plate and a large mass of cartilage extending into the metaphysis; in contrast, the rachitic-like lesion had a widened upper growth plate. Microscopic examinations of the growth plates showed a widened prehypertrophic zone for the TD-like lesion and a widened proliferative zone for the rachitic-like lesion compared with the normal growth plate.

Animals↗