1. Plasma tyrosine and phenylalanine were measured in patients with chronic renal failure and in normal subjects. Plasma tyrosine to phenylalanine ratio was greatly decreased in patients with creatinine clearance less than 16 ml/min, suggesting an impairment of phenylalanine hydroxylation. This ratio correlated with the percentage of essential to total amino nitrogen in the plasma. 2. Phenylala...

Incorporation of L-[2-2H]phenyl-[2-2H]alanine and L-phenyl-[2-13C, 15N]alanine into cytochalasin D by Zygosporium masonii involved the complete loss of both the alpha-2H- and the alpha-15N-atom. Incorporation of a mixture of L-phenyl-[15N]alanine and L-[U-14C]phenylalanine into cytochalasin D and protein amino acids (phenylalanine, leucine, isoleucine) was accompanied by a substantial loss of 1...

We have investigated the p-chlorophenylalanine-dependent loss of phenylalanine hydroxylase activity in cultured hepatoma cells. The similarity of the effect of p-chlorophenylalanine on phenylalanine hydroxylase in the hepatoma cells and that reported from studies in vivo indicates that the loss of phenylalanine hydroxylase activity is due to a direct interaction of the amino acid analogue with ...

BACKGROUND Infant nutrition has a major impact on child growth and functional development. Low and high intakes of protein or amino acids could have a detrimental effect. OBJECTIVE The objective of the study was to determine the lysine requirement of enterally fed term neonates by using the indicator amino acid oxidation (IAAO) method. L-[1-(13)C]phenylalanine was used as an indicator amino a...

Liver phenylalanine hydroxylase is allosterically activated by phenylalanine. The structural changes that accompany activation have not been identified, but recent studies of the effects of phenylalanine on the isolated regulatory domain of the enzyme support a model in which phenylalanine binding promotes regulatory domain dimerization. Such a model predicts that compounds that stabilize the r...

Phenylketonuria is the most common inborn error of metabolism. Adult patients often discontinue dietary treatment and can subsequently develop serious brain dysfunction. Some of them, however, do not present any symptoms, despite long-term exposition to high blood phenylalanine concentration. As the extent of brain toxicity of hyperphenylalaninemia is not clear in adults, new diagnostic methods...

An efficient enzymatic process was developed to produce optically pure D-phenylalanine through asymmetric resolution of the racemic DL-phenylalanine using immobilized phenylalanine ammonia-lyase (RgPAL) from Rhodotorula glutinis JN-1. RgPAL was immobilized on a modified mesoporous silica support (MCM-41-NH-GA). The resulting MCM-41-NH-GA-RgPAL showed high activity and stability. The resolution ...

Amino acids are one of the most necessary substances in intracellular metabolic processes.aromatic aminoacids such as phenylalanine and tyrosine are precursor of melanin so are important materials for the skin pigmentation.metabolic disorders in the melanin synthesis causes milky macules on the skin of patients,known as vitiligo.these patients are hypersensitive to sunlight and consequently at ...

Methods routinely utilized for detection of phenylalanine in new-born blood consist of enzymatic assays, lacking sensitivity and HPLC assays which are expensive and time-consuming to conduct. We, here, report for the first time, the construction of a phenylalanine sensitive electrode, on the basis of a selective molecularly imprinted polymer, offering sensitivity, economy and ease of use for th...