Phenylalanine hydroxylase was shown to be inhibited by oudenone and its derivatives in vitro. At a concentration of 2.3 x 10(-3) M, oudenone inhibited phenylalanine hydroxylase by 50%, and some of the oudenone derivatives showed more potent inhibition. The kinetic data have shown that the inhibition by oudenone is competitive with a tetrahydropterin cofactor (6,7-dimethyltetrahydropterin, DMPH4...

background: bone-specific alkaline phosphatase (bap) is synthesized by the osteoblasts and is presumed to be involved in the calcification of bone matrix, though its precise role in the formation process is unknown. the aim of the present study was to measure the bap activity in paget's and normal specimens by two different techniques. methods: total alp (tap) as well as bap activity-measu...

Kinetic analyses of the irreversible inhibition of L-tyrosine and L-phenylalanine transport in Bacillus subtilis by phenylalanine chloromethyl ketone revealed that the inhibition was due to an affinity labeling process. Phenylalanine chloromethyl ketone is a competetive inhibitor of L-tyrosine and L-phenylalanine transport. The K, values for irreversible inhibition of L-tyrosine and L-phenylala...

Thiobacillus neapolitanus, a strict chemoautotroph, is sensitive to the addition of 10(-4)m methionine, histidine, threonine, or phenylalanine to the thiosulfate medium on which it grows. When histidine, threonine, or phenylalanine are added at the time of inoculation, spontaneous mutants tolerant to the three amino acids are selected. These mutants appear to result from a single genetic change...

The allosteric inhibition of M1-type pyruvate kinase from rabbit skeletal muscle by phenylalanine is reciprocally dependent on Mg2+ and phosphoenolpyruvate concentrations. At pH 8, phenylalanine acts as a competitive inhibitor with respect to Mg2+ and phosphoenolpyruvate, and vice versa. Phenylalanine introduces sigmoidicity into the dependence of the reaction velocity on [Mg2+]. In vitro kinet...

The rate of release of deuterons into the body water from 2,3,4,5,6-pentadeutero-L-phenylalanine has been shown to be a valid measure of the activity of the phenylalanine hydroxylase system in vivo. At a dose of 0.5 g/kg, the rate of release of deuterons is linear for 60 to 90 min. Male rats, which had previously been shown to have 22 to 25% more phenylalanine hydroxylase activity in liver extr...