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Biomedical subjects

R W Gracy

Publications and source records attributed to R W Gracy.

At least 91 records · Page 5Linked to original sources
PubMed1978

A preparative method for the isolation of genetic variant forms of glucosephosphate isomerase and a study of five variants.

A method has been developed for the rapid, quantitative separation of normal and abnormal glucosephosphate isomerase allozymes from individuals heterozygous for genetic variant forms of the enzyme. The method utilizes a substrate gradient elution of the enzyme from carboxymethyl Biogel and is far superior in terms of resolution and recovery to methods based on electrophoresis and isoelectric focusing. Five different genetic variant forms of the enzyme were isolated and subjected to a systematic comparison of their physical, catalytic and stability properties. While the physical and catalytic properties of most of the variants were similar, clear differences in the stability of the allozymes were apparent. In order to detect mutations affecting the stability, a series of different stability tests are required.

Genetic Variation↗
PubMed1976

Isolation of rabbit muscle glucosephosphate isomerase by a single-step substrate elution.

A simple method has been developed for the rapid isolation of crystalline glucosephosphate isomerase (EC 5.3.1.9) from rabbit muscle. The enzyme is first bound to cellulose phosphate by adding the ion exchanger to a solution of the crude tissue extract. After filtering and washing the cellulose with buffer, the isomerase is specifically eluted in a batch process by its substrate, glucose 6-phosphate. The entire procedure is very rapid and results in a good recovery (at least 50%) of the enzyme with specific activity of approximately 900 units per mg. The enzyme is homogeneous by polyacrylamide gel electrophoresis in the presence of absence of sodium dodecyl sulfate and by analytical ultracentrifugation.

Animals↗
PubMed1976

Isolation and characterization of crystalline methylglyoxal synthetase from Proteus vulgaris.

Methylglyoxal synthetase, which catalyzes the conversion of dihydroxyacetone phosphate to methylglyoxal and inorganic phosphate, has been isolated and crystalized in good yields from Proteus vulgaris. The enzyme was shown to be homogeneous by a variety of criteria and was found to be a dimer (Mr = 135,000; s20,w = 7.2 S) composed of two apparently identical catalytic and physical properties and their interconvertible nature suggest that they do not represent true isozymes. The enzyme is specific for dihydroxyacetone phosphate and does not form methylglyoxal from glyceraldehyde 3-phophate, glyceraldehyde, or dihydroxyacetone. Nonphosphorylated analogs are neither substrates nor competive inhibitors, but a variety of phosphorylated analogs are competitive with respect to dihydroxyacetone phosphate. The enzyme is inhibited by inorganic orthophosphate in a complex manner which is overcome by dihydroxyacetone phosphate in a signoidal manner

Crystallization↗
PubMed1976

Structure and toxicity of alkaloids and amino acids of Sophora secundiflora.

Seeds from Sophora secundiflora were extracted into three major fractions: lipids, alkaloids, and amino acids. Most of the lipid material was composed of steroid esters. These esters were hydrolyzed, and the fatty acid compositions were determined. The major alkaloid component was cytisine, with N-methylcytisine, anagyrine, and the fatty acid compositions were determined. The major alkaloid component was cytisine, with N-methylcytisine, anagyrine, and termopsine in lower concentration. The major free ninhydrin-positive compound was gamma-glutamyltyrosine. In addition to several common amino acids, pipecolic acid and 4-hydroxypipecolic acid were identified. Both the amino acid fraction and the alkaloid fractions caused minor pharmacological disorder when injected into rats. However, when both fractions were simultaneously administered, they were lethal.

Alkaloids↗
PubMed1976

Matrix-bound phosphoglucose isomerase. Formation and properties of monomers and hybrids.

Dimeric phosphoglucose isomerase from rabbit muscle was immobilized by reaction with cyanogen-bromide-activated Sephrose 4B. The catalytic parameters and stability properties of the free and matrix-bound isomerases were essentially identical. Total monomerisation of the matrix-bound enzyme was achieved with 8 M urea as determined by a study in which one subunit was labelled with iodo[14C]acetate and the other with the 3H-labelled reagent. Although matrix-bound monomers were devoid of isomerase activity, they were still capable of binding the substrate. Matrix-bound monomers exhibited the ability to redimerize with soluble isomerase subunits from either rabbit or human yielding catalytically active dimers. Yeast isomerase monomers, in contrast, did not yield active hybrids with the rabbit monomers. Furthermore, soluble subunits, which had been inactivated with pyridoxal 5'-phosphate were also capable of hybridizing with and inducing catalytic activity in the matrix-bound monomers. These studies indicate the prerequisite of dimer formation for catalytic activity but the independent action of the catalytic centers of the dimer.

Animals↗
PubMed1975

Isolation and characterization of tissue-specific isozymes of glucosephosphate isomerase from catfish and conger.

In teleosts glucosephosphate isomerase exists as two tissue-specific isozymes. Most tissues contain the more acidic liver-type isozyme, while white muscle contains the more basic isozyme; and a few tissues contain both the liver- and muscle-type isozymes as well as a hybird. The isozymes were isolated from catfish liver and muscle and from conger muscle and shown to be homogeneous by polyacrylamide gel electrophoresis, isoelectric focusing, analytical ultracentrifugation, and rechromatography. Both isozymes are of molecular weight 132,000 (S020,w = 7.0 S) and composed of two subunits of Mr approximately 65,000. The muscle and liver isozymes were shown to have distinct isoelectric points (catfish liver = 6.2; muscle = 7.0) and amino acid compositions. Tryptic peptide maps, after S-carboxymethylation and carbamylation, revealed several distinct differences in the primary structures of the isozymes. Although the isozymes could also be distinguished on the basis of their stabilities, most of their basic catalytic properties were found to be similar. A conger was obtained which was heterozygous for the variant allele at the muscle-glucosephosphate isomerase locus. A comparison of the variant conger muscle isozyme with the wild type revealed a single altered peptide, suggesting a point mutation. The structure-function studies, as well as the genetic studies, clearly establish that the two types of isozymes are of independent genetic origin.

Alleles↗
PubMed1975

Nature of the multiple forms of sweet-potato glucose phosphate isomerase.

The previously reported isoenzymes of sweet-potato glucose 6-phosphate isomerase were resolved by DEAE-cellulose chromatography. The multiple forms exhibited identical electrophoretic properties and electrofocused as a single component with an apparent isoelectric pH of 4.0. Chromatographic studies also suggest that the multiple forms do not represent true isoenzymes.

Glucose-6-Phosphate Isomerase↗