37 research outputs found
Equisetum (horsetail) ferredoxin: characterization of the active centre and position of the four cysteine residues in this 2Fe-2S protein
Contributions of the substrate-binding arginine residues to maleate-induced closure of the active site of Escherichia coli aspartate aminotransferase.
Sequence Studies on d-Serine Dehydratase of Escherichia coli. Primary Structure of the Tryptic Phosphopyridoxyl Peptide and of the N-Terminus
Control of cell-cycle-associated tetrahydrobiopterin synthesis in rat thymocytes.
The cell-cycle progression of rat thymocytes from G0 through G1 to DNA synthesis is associated with a transient synthesis of H4biopterin, the concentration of which reaches a maximum at the time of S-phase entry and then decreases. This synthesis of H4biopterin is controlled by the specific activity of GTP cyclohydrolase I, which peaks in G1/S cells. In contrast, the catalytic activity of sepiapterin reductase remains constant throughout the cell-cycle. At G0 the steady state mRNA levels specific for GTP cyclohydrolase I and sepiapterin reductase, respectively, are below the limits of detection. Both accumulate as the thymocytes progress through the cell-cycle but lack cyclic down regulation. The data indicate that the variations in H4biopterin synthesis during the cell-cycle are caused by growth regulated increase in GTP cyclohydrolase I mRNA expression, with subsequent post-translational inactivation. This latter is likely due to the degree of enzyme phosphorylation