Conversion of a primary amine to a labeled secondary amine by the addition of phenolic group and radioiodination

To preserve the nucleophilicity of amino compounds during conjugative radioiodination, a new method for converting primary amines to phenolic secondary amines was developed. Amino acids were used as model compounds for establishing optimal conditions for the reductive amination. In the first step of the reaction, the aldehyde group of 4-hydroxybenzaldehyde (formylphenol) was reacted reversibly with an amino group to form an imine. The irreversible attachment of formylphenol to the amino group was accomplished by reduction of the imine with sodium cyanoborohydride. The pH optimum for the reaction was 5.0. Higher temperature has favorable effects on the rate and extent of the conjugation. Phenolic derivatives of amino compounds suitable for radioiodination are produced by the reactions described.     

Genetic characterization of mouse immunoglobulin allotypic determinants (allotopes) defined by monoclonal antibodies

We have generated a new series of monoclonal antibodies recognizing allotypic determinants on mouse IgG₁, IgG_2a, and IgG_2b. In this communication we describe their reactivities with immunoglobulins of the inbred mouse strains. Comparison with serology charts indicates that many of these monoclonal antibodies detect allotypic specificities previously defined by conventional antisera; others define previously undescribed specificities. Strain and isotype distribution allows us to assign five new allotypic specificities to Igh-1 and three new specificities to Igh-3. In addition, on the basis of reactivity with the monoclonal antibodies, we have defined a new Igh haplotype in SWR/J mice, Igh ^p.Abbreviations used in this paper Igh immunoglobulin heavy chain - SDS sodium dodecyl sulfate     

Monoclonal antibodies to neurospora adenylate cyclase

A monoclonal antibody against $\text{Neurospora}$ soluble adenylate cyclase was obtained. The antibody inhibits cyclase activities from several lower eucaryotic organisms but not activities associated to testicular cytosol or turkey erythrocyte membranes.     

NADPH/NADP+ ratio: regulatory implications in yeast glyoxylic acid cycle

Summary The utilization by yeast of two carbon sources is carried out through the operation of the glyoxylic acid cycle. Kinetic data from the isocitrate transforming enzymes suggest that the flow of isocitrate through the glyoxylic acid cycle depends upon the inhibition of the isocitrate decarboxylating enzymes. Both isocitrate dehydrogenases are inhibited by a mixture of glyoxylate + oxaloacetate, but for the reasons described in the text we consider that this inhibition is of no physiological significance. On the other hand, we have found that NADPH is a competitive inhibitor of NADP-isocitrate dehydrogenase with respect to NADP⁺, with a K_I similar to its K_M. It also produces an additive effect on the NADH-produced inhibition of NAD-isocitrate dehydrogenase. We propose NADPH as the compound that channels the utilization of isocitrate into the glyoxylic acid cycle. This is supported by the finding of an increased NADPH/NADP⁺ ratio in acetate grown yeast with respect to glucose grown cells.     

The isolation and properties of phenylalanine hydroxylase from human liver

Phenylalanine hydroxylase was prepared from human foetal liver and purified 800-fold; it appeared to be essentially pure. The phenylalanine hydroxylase activity of the liver was confined to a single protein of mol.wt. approx. 108000, but omission of a preliminary filtration step resulted in partial conversion into a second enzymically active protein of mol.wt. approx. 250000. Human adult and full-term infant liver also contained a single phenylalanine hydroxylase with molecular weights and kinetic parameters the same as those of the foetal enzyme; foetal, newborn and adult phenylalanine hydroxylase are probably identical. The K(m) values for phenylalanine and cofactor were respectively one-quarter and twice those found for rat liver phenylalanine hydroxylase. As with the rat enzyme, human phenylalanine hydroxylase acted also on p-fluorophenylalanine, which was inhibitory at high concentrations, and p-chlorophenylalanine acted as an inhibitor competing with phenylalanine. Iron-chelating and copper-chelating agents inhibited human phenylalanine hydroxylase. Thiol-binding reagents inhibited the enzyme but, as with the rat enzyme, phenylalanine both stabilized the human enzyme and offered some protection against these inhibitors. It is hoped that isolation of the normal enzyme will further the study of phenylketonuria.     

Identification and genetic control of starch-degrading enzymes in maize endosperm

Three starch-degrading enzymes from liquid endosperm of maize have been separated by means of horizontal acrylamide gel electrophoresis. The three enzymes are tentatively identified as -amylase (zone 1), -amylase (zone 2), and -glucan phosphorylase (zone 3). Electrophoretic variants of these enzymes were found among ten inbred strains examined. Results of genetic crosses with respect to zone 2 amylase show that it is controlled by a pair of alleles (Amy-2 ^A and Amy-2 ^B) acting without dominance. It further appears that Amy-2 and Ct (catalase) are linked with 5% recombination frequency.This work was supported by the U.S. Atomic Energy Commission, under contract No. AT(11-1)-1338.