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...

Some D-amino acids such as d-tryptophan and D-phenylalanine are well known as naturally-occurring sweeteners. Photoreactive D-phenylalanine derivatives containing trifluoromethyldiazirinyl moiety at 3- or 4-position of phenylalanine, were designed as sweeteners for functional analysis with photoaffinity labeling. The trifluoromethyldiazirinyl D-phenylalanine derivatives were prepared effectivel...

FREATMENT of phenylketonuric infants with low phenylalanine diet requires frequent measurements of blood phenylalanine, since diet must be adjusted to changing phenylalanine requirements. The amount of blood required for repetitive determinations by the usual methods may be excessive. The need for frequent and rapid determinations led us to modify the method for serum phenylalanine (1) to permi...

Using evolved pyrrolysyl-tRNA synthetase-tRNA(CUA)(Pyl) pairs, L-phenylalanine, p-iodo-L-phenylalanine and p-bromo-L-phenylalanine have been genetically incorporated into proteins at amber mutation sites in E. coli.

BACKGROUND Women with untreated phenylketonuria (PKU) often have poor reproductive outcomes. OBJECTIVE We assessed the effects of intakes of major nutrients on plasma phenylalanine concentrations and we measured phenylalanine hydroxylase activity and phenylalanine intakes in pregnant women with PKU. DESIGN Dietary intakes and plasma phenylalanine concentrations were compared in 4 subject gr...

Cloning and expression of the L-phenylalanine dehydrogenase gene, from B. sphaericus in E. coli were done. The gene was cloned in the vector pET16b and transformed into E. coli BL21 (DE3). The functional form of the L-phenylalanine dehydrogenase enzyme was purified by affinity purification techniques, taking advantage of the ability of this enzyme to bind to the nucleotide site affinity dye, Re...

Enzymatic cycling assays for the determination of L-phenylalanine and phenylpyruvate in deproteinized tissue extracts are described. Assay 1 couples glutamine transaminase K with L-phenylalanine dehydrogenase. Assay 2 combines phenylalanine dehydrogenase, L-amino acid oxidase, and catalase. In both assays, tyrosine and some other amino acids (or their alpha-keto acid analogs) can replace phenyl...

To establish an advantageous method for the production of l-amino acids, microbial isomerization of d- and dl-amino acids to l-amino acids was studied. Screening experiments on a number of microorganisms showed that cell suspensions of Pseudomonas fluorescens and P. miyamizu were capable of isomerizing d- and dl-phenylalanines to l-phenylalanine. Various conditions suitable for isomerization by...

A patient with atypical phenylketonuria (defective BH2 synthesis), detected at age 6 months because of severe muscle hypotonia and serum phenylalanine of 20 mg/100 ml, had normal activities of phenylalanine-4-hydroxylase and DHPR in liver biopsy, but only 2% activity in the phenylalanine-4-hyroxylase in vivo test using deuterated phenylalanine. After IV administration of 2.5 mg/kg chemically pu...