Max E. Rafelson

Isolation and characterization of two structural isomers of N-acetylneuraminyllactose from bovine colostrum

Abstract A method has been described for the isolation of two structural isomers of N-acetylneuraminyllactose from bovine colostrum. The two isomers were shown to be N- acetylneuraminyl -(2 → 3)-β- D - galactopyranosyl -( I → 4)- D - glucopyranose and N- acetylneuraminyl -(2 → 6)- D - galactopyranosyl -( I → 4)- D - glucopyranose . The latter isomer had not previously been reported to occur in bovine milk or colostrum. Although both isomers were cleaved completely by the purified neuraminidase (EC 3.2.1.18) from influenza virus, the isomers differed in their pH optimum, Km and V. The mode of linkage of N-acetylneuraminic acid to lactose appears to influence both the rate of formation and breakdown of the enzyme-substrate complex.

Studies on the neuraminidase of influenza virus. I. Separation and some properties of the enzyme from Asian and PR8 strains.

Abstract A method for the separation of neuraminidase from the Asian and PR8 strains of influenza virus has been described. The procedure involves treatment of preparations of virus or vaccine with trypsin, followed by dialysis and centrifugation to remove the remainder of the virus particle. The neuraminidase preparations do not agglutinate red blood cells nor do they prevent their agglutination by Lee “indicator” virus. N -Acetylneuraminic acid is liberated from neuramin lactose and orosomucoid by the neuraminidase preparations. Some preliminary studies on the kinetic properties of the enzyme have been presented.

STUDIES ON THE NEURAMINIDASE OF INFLUENZA VIRUS. II. ADDITIONAL PROPERTIES OF THE ENZYMES FROM THE ASIAN AND PR 8 STRAINS.

Abstract A comparison of the properties of purified neuraminidases from the Asian and PR 8 strains of influenza virus has shown a number of differences. The enzymes differ in their K M values for N -acetylneuraminyllactose, in their K I values for the competitive inhibitor N -acetylneuraminic acid, in heat stability, and in their pH optimum for a number of substrates. Preliminary studies indicate that the two enzymes are immunologically distinguishable, and the degree of neutralization of enzyme action by specific antiserum is dependent on the substrate employed.

Some hydrodynamic properties of human transferrin

The molecular weight of iron-free human transferrin, type C, was 92,000–95,000. Its diffusion constant and intrinsic viscosity at pH 5.0 were 5.30 × 10−7 and 0.046, respectively. The hydrodyanmic information available indicated that transferrin is a prolate molecule with an axial ratio of 1:3 and a hydration of 0.6 gm water per gram protein.

Studies on the neuraminidases of influence virus III. Stimulation of activity by bivalent cations

Abstract Bivalent cations (Ca 2+ , Mn 2+ and Mg 2+ ) have been shown to stimulate the activity of the purified neuraminidases ( N -acetylneuraminate glycohydrolase, EC 3.2.1.18) from influenza virus although an absolute requirement could not be demonstrated. This stimulation is dependent upon the enzyme and is independent of the substrate and the nature of the linkage of the N -acetylneuraminic acid. The addition of Ca 2+ increases the v max but has no effect on the K m of the reaction.

The biosynthesis of leucine in Aerobacter aerogenes

Abstract Leucine was isolated from Aerobacter aerogenes grown on media containing acetate-1-C14, glucose-1-C14, glucose-2-C14, glucose-3,4-C14, or glucose-1-C14 plus unlabeled acetate. The distributions of radioactivity in the individual carbon atoms of leucine indicated that carbon atoms 1 and 2 of leucine were derived from an acetate unit, and that the remaining four carbon atoms were derived from carbon atoms 1 and 2 of glucose. These data indicate that the pathway for the biosynthesis of leucine in A. aerogenes is similar to that in E. coli, T. utilis, Neurospora, and S. cerevisiae (1–5).

Studies on the metabolism of virus-infected tissues. II. The effect of influenza virus on ribonucleotide metabolism in chick chorio-allantoic membranes.

Abstract The propagation of influenza A virus in isolated chick chorio-allantoic membranes is associated with an increased metabolic activity of the acid-soluble purine ribonucleoside 5′-phosphates of the host tissue. The virus-infected tissue showed an increased incorporation of glycine-1-C 14 and formate-C 14 into purine ribonucleoside 5′-phosphates. In tissues prelabeled with glycine-1-C 14 , the addition of virus increased the loss of radioactivity from ribonucleic acid (RNA) and the purine ribonucleoside 5′-phosphates investigated. l -Azaserine completely prevented the incorporation of formate-C 14 and glycine-1-C 14 into RNA and acid-soluble purine ribonucleoside 5′-phosphates while having no effect on virus propagation. Azaserine was found to enhance the utilization of adenine-8-C 14 by this system. The possible implications of these results are discussed.

Studies on the metabolism of virus-infected tissues. I. Free amino acid metabolism in chick chorioallantoic membranes infected with influenza virus☆

Abstract The propagation of influenza A virus in isolated chick chorio-allantoic membranes is associated with an increased metabolic activity of the free amino acids of the host tissue. The virus-infected tissue showed an increased conversion of glucose-C 14 to glutamic acid, aspartic acid, serine, alanine, and glycine. In tissues prelabeled with glycine-C 14 or alanine-C 14 , the addition of virus increased the rate of loss of radioactivity from the free glycine or free alanine, but had no effect on the loss of radioactivity from the corresponding protein-bound amino acids. Virus propagation had no effect on the rate of incorporation of several C 14 amino acids into the mixed proteins of the chorio-allantoic membranes. The possible implications of these results are discussed.

Studies on the metabolism of virus-infected tissues. III. The effect of influenza virus on ribonucleic acid fractions of chick chorio-allantoic membranes

Abstract Chromatography on cellulose ion-exchange columns of ribonucleic acid of (RNA) extracted by phenol from isolated chick chorio-allantoic membranes yielded a number of RNA fractions which exhibited differential rates of incorporation of glycine-1-C 14 and adenine-8-C 14 . Propagation of influenza A virus in this tissue was associated with an alteration both in the metabolic behavior and Chromatographic behavior of the RNA fractions isolated. The base composition of certain of the RNA fractions were considerably altered in the virus-infected tissue.