PubMed Health⌕ Search

Biomedical subjects

R W Erbe

Publications and source records attributed to R W Erbe.

45 records · Page 3Linked to original sources
PubMed1973

Regulation of 5-methyltetrahydrofolate: homocysteine methyltransferase activity by methionine, vitamin B12, and folate in cultured baby hamster kidney cells.

Rapid growth of BHK cells in methioninedeficient medium required supplementation with homocysteine, B(12), and over 40-fold greater levels of folic acid than growth in methionine-supplemented medium. The activity of the B(12)-dependent 5-methyltetrahydrofolate: homocysteine methyltransferase was studied in extracts of BHK cells grown in media containing various concentrations of the compounds of the enzyme reaction. The methyltransferase activity increased over 4-fold when B(12)-deficient deficient medium was supplemented with optimal levels of B(12); this increase was not prevented by puromycin. Addition of homocysteine to growth medium containing methionine, B(12), and folic acid was without effect. However, methyltransferase activity increased 2.5- to 4.0-fold further beyond the highest levels obtained in the presence of methionine, B(12), and folic acid when homocysteine was substituted for methionine in the growth medium. This increase was blocked by puromycin and was not due to removal of feedback inhibition of activity by the product methionine. These results suggest that methyltransferase activity may be regulated in part by derepression of the enzyme's synthesis on substitution of the substrate homocysteine for the product methionine.

Animals↗
PubMed1972

Lysyl-protocollagen hydroxylase deficiency in fibroblasts from siblings with hydroxylysine-deficient collagen.

Cell culture studies were performed on members of a family in which two sisters, ages 9 and 12, have a similar disorder characterized clinically by severe scoliosis, joint laxity and recurrent dislocations, hyperextensible skin, and thin scars. The skin collagen from the sisters was markedly deficient in hydroxylysine, but other amino acids were present in normal amounts. Hydroxylysine in collagen from fascia and bone was reduced to a lesser extent. Since the most likely explanation for the hydroxylysine deficiency was a reduction in enzymatic hydroxylation of lysine residues in protocollagen, we measured the activity of lysyl-protocollagen hydroxylase in crude lysates of cultured skin fibroblasts. Enzyme activities in the two affected children were 14 and 10% of controls, whereas the activity was about 60% of normal in the mother, a pattern most consistent with autosomal recessive inheritance. The mutant enzyme demonstrated the same cofactor requirements as that from normal cells. Deficiency of lysyl-protocollagen hydroxylase is the first inborn error of human collagen metabolism to be defined at the biochemical level.

Adolescent↗