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P G Richman

Publications and source records attributed to P G Richman.

12 recordsLinked to original sources
PubMed1988

A procedure for total protein determination with special application to allergenic extract standardization.

A method for total protein determination of allergenic extracts has been developed and evaluated. Samples were hydrolyzed with 5 M NaOH followed by colorimetric determination with ninhydrin of the released amino acids using bovine serum albumin as the standard. The entire procedure was carried out in disposable plastic tubes. Substances (glycerol, phenol and mannitol) commonly present in allergenic extracts manufactured for human use did not affect the assay results. Analyses of four different pollen extracts by the method gave good agreement with amino acid analyses. Other methods of analysis (total N, protein N unit assay, Lowry) gave more variable results compared with amino acid analysis. Analysis of the total protein content of 53 different lots of allergenic extracts gave narrow ranges of values for each species. Standardized mite extracts analyzed for total protein by US FDA-licensed manufacturers using this assay showed a good correlation of biological activity with total protein.

Allergens↗
PubMed1984

The important sources of German cockroach allergens as determined by RAST analyses.

The important sources of allergens in cockroach were investigated. Aqueous extracts were prepared from American and German cockroach whole body, cast skins, and feces as well as egg shells of German cockroach. Each extract was analyzed for protein content and characterized by electrophoretic analyses. Cockroach specific IgE in the sera of patients and controls was investigated by RAST, by use of paper discs coupled to equal amounts of protein from each extract. The results for German cockroach indicate that whole body and cast skins have equal RAST potencies, egg shells are less potent, and feces are least potent. Reactivity of the same individuals to American cockroach was much lower. RAST-inhibition studies with German cockroach extracts indicate that the same allergens are found in whole body, cast skins, egg shells, and feces. The RAST potencies obtained in the inhibition experiments, in general, agreed with the direct RAST results. The results indicate that cast skins and whole bodies of German cockroaches contain the clinically relevant allergens for this group of cockroach-sensitive patients.

Allergens↗
PubMed1980

Calmodulin.

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3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1979

Specific perturbation by Ca2+ of tyrosyl residue 138 of calmodulin.

Calmodulin that was selectively nitrated at tyrosyl residue 99 or 138 was used as a regional spectral probe of the structural changes associated with Ca2+ or Mg2+ binding to the protein. Perturbations of the spectral properties of the nitrotyrosyl residues correlated well with those of the tyrosyl residues in unmodified calmodulin. The spectral properties of tyrosyl residue 99 were sensitive to ionic strength, but not to Ca2+ binding to the protein. The spectrum of tyrosyl residue 138, in contrast, was markedly affected both by ionic strength and Ca2+ binding. Although Mg2+ caused spectral changes, they were clearly different from those produced by Ca2+ and resembled instead the less specific changes elicited by Na+. Conformational changes associated with Ca2+ but not Mg2+ binding to calmodulin seem to affect selectively the microenvironment around tyrosyl residue 138.

Calcium↗
PubMed1978

Interaction of 125I-labeled Ca2+-dependent regulator protein with cyclic nucleotide phosphodiesterase and its inhibitory protein.

The Ca2+-dependent regulator protein of cyclic nucleotide phosphodiesterase was labeled with 125I to the extent of 1 mol of monoiodotyrosine per mol. The iodinated protein showed a small decrease in affinity for phosphodiesterase but gave the same maximal level of activation of the enzyme as did the unmodified regulator protein. Iodinated regulator protein formed complexes with both highly purified cyclic nucleotide phosphodiesterase and phosphodiesterase inhibitory protein in the presence but not in the absence of Ca2+ as demonstrated by ultracentrifugation in glycerol gradients. Cross-linking experiments indicate that the Ca2+-dependent regulator protein interacts with the large subunit of the inhibitory protein.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1976

Hydrolysis and transpeptidation of peptide substrates by acetyl-pepsin.

Treatment of swine pepsin with acetylimidazole to acetylate approximately five of its 16 tyrosyl residues causes a significant enhancement of catalytic efficiency (kcat/Km) toward substrates such as dansyl-glycyl-glycyl-L-phenylalanyl-L-phenylalanine 3-(4-pyridyl)propyl ester and benzyloxy-carbonyl-(glycyl)n-p-nitroLphenylalnyl-Lphenylalanyl-L-tyrosine (where n = 0, 1,2). Stopped-flow kinetic studies, under conditions of enzyme excess, with the dansyl peptide have shown that, as with untreated pepsin, the rate-limiting step in the over-all catalytic process is associated with the decomposition of the first detectable enzyme-substrate complex, whose dissociation constant is approximately equal to the Km found in steady-state kinetic experiments. With substrates of the type benzoyl-(glycyl)n-nitro-L-phenylalanyl-L-tyrosine, an increase in the chain length of the peptide leads to an increase in the value of kcat/Km, supporting the view that secondary enzyme-substrate interactions may produce at the extended active site conformational changes that are reflected in higher catalytic efficiency. This effect is more marked with acetyl-pepsin than with untreated pepsin, and suggests that the conformational mobility of the active site is increased by partial acetylation. Acetyl-pepsin is less effective than untreated pepsin in catalyzing transpeptidation reactions in which acetyl-L-phenylalanyl-L-tyrosine and benzyloxycarbonyl-(glycyl)n-p-nitro-L-phenylalanine are the reactants; this finding is consistent with the more rapid hydrolysis of the product of transpeptidation.

Acetylation↗
PubMed1975

Regulation of gamma-glutamyl-cysteine synthetase by nonallosteric feedback inhibition by glutathione.

Gamma-Glutamyl-cysteine synthetase is inhibited by glutathione under conditions similar to those which prevail in vivo, thus strongly suggesting a physiologically significant feedback mechanism. Inhibition by glutathione, which is not allosteric, appears to involve the binding of glutathione to the glutamate site of the enzyme as well as to another enzyme site; the latter binding appears to require a sulfhydryl group since ophthalmic acid (gamma-glutamyl-alpha-aminobutyryl-glycine) is only a weak inhibitor. The finding that glutathione regulates its own synthesis by inhibiting synthesis of gamma-glutamyl-cysteine appears to explain observations on patients with 5-oxoprolinuria, who were shown to have a block in the gamma-glutamyl cycle consisting of a marked deficiency of glutathione synthetase and consequently of glutathione. These patients produce greater than normal amounts of gamma-glutamyl-cysteine, which is converted by the action of gamma-glutamyl cyclotransferase to 5-oxoproline; production of the latter compound exceeds the capacity of 5-oxoprolinase to convert it to glutamate. The apparent Km value for L-cysteine for gamma-glutamyl-cysteine synthetase (0.35 mM) is not far from intracellular concentrations of L-cysteine suggesting that the availability of L-cysteine may also play a role in the regulation of glutathione synthesis.

Allosteric Regulation↗