Studies in the biosynthesis of vitamin B12

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references.The Pseudomonas denitrificans coba and the Salmonella typhimurium cbid genes were overexpressed in the heterologous E.coli system. The function of P.denitrificans coba gene product was identified as S-adenosyl methionine dependent methyl transferase catalyzing the C-2 and C-7 methylations of Uroporphyrinogen III to precorrin-2, without performing an extra methylation at C-12 of precorrin-2 to trimethylpyrrocorphin. The function of the S.typhimurium cbid gene product has not yet been identified. The C-terminus of the EColi cysg was shown to be a S-adenosyl methionine dependent methyltransferase catalyzing the C-2 and C-7 methylations of Uroporphyrinogen III to precorrin-2. The C-terminus of cysg was able to perform the extra methylation at C-12 of precorrin-2 to give trimethylpyrrocorphin. The C-terminus of cysg was not involved in the transformation of precorrin-2 to siroheme. The structures of the enzymatic reactions were identified by the use of 13C NMR

Compartmentation of glycolysis and glycogenolysis in the perfused rat heart

Developing methods that can detect compartmentation of metabolic pathways in intact tissues may be important for understanding energy demand and supply. In this study, we investigated compartmentation of glycolysis and glycogenolysis in the isolated perfused rat heart using 13C NMR isotopomer analysis. Rat hearts previously depleted of myocardial glycogen were perfused with 5.5 mm [U-13C]glucose plus 50 mU/mL insulin until newly synthesized glycogen recovered to new steady-state levels (sim60% of pre-depleted values). After a short wash-out period, the perfusate glucose was then switched to [1-13C]glucose, and glycolysis and glycogenolysis were stimulated by addition of glucagon (1 mug/ml). A 13C NMR multiplet analysis of the methyl resonance of lactate provided an estimate of pyruvate derived from glucose vs glycogen while a multiplet analysis of the C4 resonance of glutamate provided an estimate of acetyl-CoA derived from glycolytic pyruvate vs glycogenolytic pyruvate. These two indices were not equivalent and their difference was further magnified in the presence of insulin during the stimulation phase. These combined observations are consistent with functional compartmentation of glycolytic and glycogenolytic enzymes that allows pyruvate generated by these two processes to be distinguished at the level of lactate and acetyl-CoA. Copyright © 2004 John Wiley & Sons, Ltd

Interpolation Problems For Hilbert-Schmidt Operators In Reflexive Algebras

WOS: A1993MG9860000