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Query: EC:4.1.1.17 (ornithine decarboxylase)
 6,351 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Ornithine decarboxylase (L-ornithine carboxylase, EC 4.1.1.17) is an important enzyme in polyamine synthesis. Its activity is influenced by several peptides hormones, including growth hormones, which have physiological significance in various growth situations. A crude ovine pituitary growth hormone preparation (NIH-GH-S10) was subjected to gel exclusion chromatography (Sephadex G-100) and two major fractions were obtained. One of these corresponded to dimeric growth hormone (GH). The other fraction was excluded by the gel matrix, suggesting a material of higher molecular weight than GH. This was confirmed by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. Analysis of a high molecular weight fraction by radioimmunoassay (antisera prepared against GH) and by bioassay (weight gain in hypophysectomized rats) gave apparent GH contents of 19% and 6%, respectively. On a weight basis, the high molecular weight fraction was more effective than GH in stimulating the activity of hepatic and adrenal ornithine decarboxylase, but GH was more effective in stimulating renal ornithine decarboxylase activity. Subfractionation of the high molecular weight fraction using a high porosity gel (Sephadex G-200) gave four fractions, which were shown by amino acid analysis and by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate to be distinct from GH and heterogenous. These subfractions had different potencies for stimulating renal and hepatic ornithine decarboxylase activity. The ability of crude growth hormone preparations to stimulate ornithine decarboxylase activity in some tissues may be a function of pituitary factors, in addition to GH, which have minimal growth promoting activity.
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PMID:Tissue-specific stimulation of ornithine decarboxylase activity by pituitary factors immunologically related to growth hormone. 83 33

We find that the transcription of various ribosomal proteins can be differentially affected by polyamines and by changes in growth rates. Using strain MG1655 of Escherichia coli K-12 (F-, lambda-), we have determined the effects of polyamines and changes in growth rate on the transcription of several ribosomal genes and the polyamine-synthesizing enzymes ornithine decarboxylase (L-ornithine carboxy-lyase; EC 4.1.1.17) and arginine decarboxylase (L-arginine carboxylyase; EC 4.1.1.19). Ribosomal proteins S20 and L34 can be differentiated from the other ribosomal proteins studied; the transcription of S20 and L34 is especially sensitive to polyamines and less sensitive to changes in growth rates. In contrast, the transcription of S10, S15, S19, L2, L4, L20, L22, and L23 is insensitive to polyamines although it is particularly sensitive to changes in growth rates. Like S20 and L34, the transcription of ornithine decarboxylase and arginine decarboxylase is especially sensitive to polyamines. Polyamines specifically enhance the transcription of ribosomal proteins S20 and L34, and decrease that of ornithine decarboxylase and arginine decarboxylase. It is evident that polyamines can exert both positive and negative regulation of gene expression in E. coli that can be differentiated from the effects caused by changes in growth rates.
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PMID:Transcriptional effects of polyamines on ribosomal proteins and on polyamine-synthesizing enzymes in Escherichia coli. 218 70

Escherichia coli ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) was found to be inhibited by several basic proteins. When ribosomal proteins were tested, major ribosomal proteins, with the exceptions of S1, S5, S6, S8, S10, L3, L5, L6, L7/L12, L8, L9 and L10 proteins, showed antizyme activity in addition to the recognized antizymes (S20/L26 and L34 proteins). Furthermore, it was found that L20 protein and a new ribosomal protein, tentatively named X1 protein and bound to 50 S ribosomal subunits, showed stronger antizyme activity than S20/L26 and L34 proteins. The antizyme activity of S20/L26 and L34 proteins was at most 10% of the total antizyme activity of ribosomal proteins. Several basic polypeptides also showed antizyme activity in the order polyarginine greater than protamine greater than histone greater than polylysine. Ribosomal proteins and basic polypeptides inhibited ornithine decarboxylase activity competitively. Ribosome-bound antizymes were inactive as antizymes, and antizyme inhibition of ornithine decarboxylase was eliminated by ribosomes. When E. coli extracts were separated into ribosomes and 100,000 X g supernatant fraction, no significant antizyme activity was observed in the supernatant fraction. Results of these in vitro experiments infer that basic antizymes may not function as inhibitors of ornithine decarboxylase in vivo.
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PMID:Nonspecific inhibition of Escherichia coli ornithine decarboxylase by various ribosomal proteins: detection of a new ribosomal protein possessing strong antizyme activity. 354 48