Biomedical subjects

C M Edson

Publications and source records attributed to C M Edson.

21 records · Page 2Linked to original sources

PubMed1977

Purification and properties of poly(adenosine diphosphate ribose) synthetase.

Poly(ADP-ribose) synthetase has been purified approximately 5000-fold from rat liver nuclei. The activity of the purified enzyme is absolutely dependent upon the presence of native or synthetic DNA, and the further addition of histone(s) stimulates the activity 3- to 5-fold. When the ADP-ribosylated material synthesized in the absence or presence of various histones is analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the major product in all cases migrates between histones H1 and H3-H2B with the same RF value of 0.58 relative to the marker dye. No ADP-ribose was found to co-electrophorese with any of thehistones. The addition of histones does not affect the chain number of the poly(ADP-ribose) synthesized but does result in an increase in the average chain length of the polymer. In the presence of histones, the Km for NAD+ decreases from 80 micron to 25 micron and the Vmax doubles. These results indicate that, in the purified poly(ADP-ribose) synthetase system, histones are not ADP-robosylated but act as allosteric activators.

Animals↗

PubMed1976

Biochemical and genetic studies on galactosamine metabolism in Neurospora crassa.

In Neurospora, galactosamine can be released from the cell wall and from an alcohol-soluble compound by acid hydrolysis. All of the detectable alcohol-soluble galactosamine was present as uridine diphospho-2-acetamido-2-deoxy-D-galactose (UDPGalNAc). The results of pulse-labeling studies and enzymatic assays indicated that UDPGalNAc was synthesized via the epimerization of uridine diphospho-2-acetamido-2-de+xy-D-glucose (UDPGlcNAc). A single-gene morphological mutant, doily (do), which grew at less than 4% the rate of the wild-type strain, had 3% of the wild-type UDPGalNAc content and 0.5% of the wild-type level of cell wall galactosamine but normal levels of UDPGlcNAc and cell wall glucosamine. Cell extracts of the doily cultures containing only 20% of the specific activity of UDPGlcNAc-4-epimerase found in the extracts of wild-type cultures. Two types of faster-growing partial revertants of the doily strain were isolated. One type had an intermediate level of both alcohol-soluble and cell wall galactosamine. A second type had an intermediate level of alcohol-soluble galactosamine but low levels of cell wass galactosamine. Genetic analyses indicated that the reverse mutations had occurred at the do locus in both types. This finding that cell wall glucosamine synthesis and growth rate can be separated genetically indicates that mutations at the do lucus lead to pleiotropic effects.

Carbohydrate Epimerases↗

PubMed1975

Changes in glucosamine and galactosamine levels during conidial germination in Neurospora crassa.

The levels of glucosamine and galactosamine were determined in conidia, germinating conidia, and vegetative mycelia of Neurospora crassa. In the vegetative mycelia about 90% of the amino sugars were shown to be components of the cell wall. The remaining 10% of the amino sugars were tentatively identified as the nucleotide sugars uridine diphospho-2-acetamido-2-deoxy-D-glucose and uridine diphospho-2-acetamido-2-deoxy-D-galactose. Conidia and vegetative mycelia contained about the same levels of glucosamine. During the first 9 h after the initiation of germination, the total glucosamine content had increased 3.1-fold, whereas the residual dry weight of the culture had increased 7.7-fold. This led to a drop in the glucosamine concentration from 100 mumol/g of residual dry weight to 42 mumol/g. During this time, all of the conidia had germinated and the surface area of the new germ tubes had increased to 10 times that of the conidia. Either germ tubes were initially produced without glucosamine-containing polymers, or these polymers (probably chitin) were deposited only at low densities in the germ tube cell walls. The chitin precursor uridine diphospho-2-acetamido-2-deoxy-D-glucose was present at all times during conidial germination. Conida contained very low levels of galactosamine. During germination, galactosamine could not be detected until the culture had reached a cell density of about 0.6 mg of residual dry weight per ml of growth medium. This was observed regardless of the time required to reach this cell density or the fold increase in dry weight. The accumulation of galactosamine-containing polymers does not appear to be necessary for germ tube formation. The levels of soluble galactosamine (uridine diphospho-2-actamido-2-deoxy-D-galatose) were very low in conidia and increased during germination at the same time that galactosamine appeared in the cellular polymers. In addition, under certain culture conditions, the appearance of galactosamine and the increase in the glucosamine concentration occurred simultaneously.

Autoanalysis↗