The quenching of the Y(D)(.) tyrosyl radical in photosystem II by nitric oxide was reported to result from the formation of a weak tyrosyl radical-nitric oxide complex (Petrouleas, V., and Diner, B. A. (1990) Biochim. Biophys. Acta 1015, 131-140). This radical/radical reaction is expected to generate an electron spin resonance (ESR)-silent 3-nitrosocyclohexadienone species that can reversibly r...

The kinetic (KIE) and solvent (SIE) isotope effect methods were used to investigate the mechanism of enzymatic hydroxylation of halogenated derivatives of l-tyrosine to l-DOPA catalyzed by the enzyme tyrosinase (EC 1.14.18.1). The values of deuterium KIE and SIE were obtained using the non-competitive method with spectrophotometric measurements. The Lineweaver-Burk plots were used for determina...

Topica! tyrosine has been proposed as a tanning accelerator because tyrosine is a precursor of melanin. We tested formulations containing O, 1, and 2% L-tyrosine topically on 14 individuals daily for 28 days. Percutaneous absorption using "C tyrosine was 1.23% in 24 hr. No enhanced pigmentation was clinically evident in any of the subjects. In this study, we were unable to demonstrate that topi...

Background: L-tyrosine adenylation is a key step in aminocoumarin antibiotic and vancomycin biosynthesis. Results: Several, but not all tyrosine-adenylating enzymes require MbtH-like proteins for activity, forming heterotetrameric complexes. A single L→M mutation creates an MbtH-independent enzyme. Conclusion and Significance: MbtH-like proteins are essential tools in the combinatorial biosynth...

6-[(18)F]Fluoro-m-tyrosine (FMT) is a positron emission tomography (PET) imaging agent for the aromatic L-amino acid decarboxylase enzyme. Its parent compound, L-m-tyrosine (LMT) induces behavioral effects in rodents via dopamine release. To assess the potential pharmacologic effect of FMT, its role in dopamine release and metabolism in rat striatum was compared with LMT and L-DOPA using in viv...

Thank you for the opportunity to respond to the letter by McKay and colleagues, which argued that the studies in our paper failed to consider a critical design flaw since the culture medium in which our cells were grown contained tyrosine, complicating interpretation of our data. Prior to performing the reported experiments, we compared the effect of tyrosine in the culture medium. Heterologous...

Through the strategic design of ligands based on amino acids, structural diversity in chiral coordination architectures of CuII is demonstrated with six new examples: {[Cu(L-HTyrbenz)2]·CH3OH·H2O}n (1), {[Cu(L-HSerbenz)2]·3H2O}n (2), {[Cu(L-HTyrthio)2]·H2O}n (3), [Cu(L-HTyr4-pyr)2(H2O)]·2H2O (4), [Cu(L-HSerthio)2(H2O)] (5), and [Cu(L-Phethio)2(H2O)]·3H2O (6) [where L-H2Tyrbenz = L-N-(benzyl)-ty...

To guarantee specific tRNA and amino acid pairing, several aminoacyl-tRNA synthetases correct aminoacylation errors by deacylating or "editing" misaminoacylated tRNA. A previously developed variant of Escherichia coli tyrosyl-tRNA synthetase (iodoTyrRS) esterifies or "charges" tRNA(Tyr) with a nonnatural amino acid, 3-iodo-l-tyrosine, and with l-tyrosine less efficiently. In the present study, ...

Previous studies have implicated receptor tyrosine kinases in progesterone-induced [Ca2+]i signalling, and consequent induction of the acrosome reaction, in human spermatozoa. We have investigated the effects of tyrosine kinase inhibition on [Ca2+]i responses in large numbers of individual human spermatozoa. Genistein (5, 50 and 250 micromol/l), an inhibitor of receptor-linked tyrosine kinases,...

fms-like tyrosine kinase-3 is a receptor tyrosine kinase expressed by immature hematopoietic cells and is important for the normal development of stem cells and the immune system. mutations of fms-like tyrosine kinase-3 have been detected in about 30% of patients with acute myelogenous leukemia and a small number of patients with acute lymphoblastic leukemia. the fms-like tyrosine kinase-3 muta...