Exogenous addition of copper stimulates cellular differentiation in Streptomyces spp. Several lines of evidence suggested a parallel correlation between the stimulatory effect of copper and phenol-oxidizing enzyme activities in Streptomyces griseus. Here a novel extracytoplasmic phenol oxidase (EpoA) associated with cellular development of this organism was identified and characterized. EpoA ac...

Monoaminergic neurons use dopa decarboxylase (DDC; aromatic-L-amino-acid carboxy-lyase, EC 4.1.1.28) to form dopamine from L-3,4-dihydroxyphenylalanine (L-dopa). We measured regional dopa decarboxylase activity in brains of six healthy volunteers with 6-[18F]fluoro-L-dopa and positron emission tomography. We calculated the enzyme activity, relative to its Km, with a kinetic model that yielded t...

Background: Melanomas arise from multipotent neural crest derivative, the melanocytes. At the tumor-stroma interphase, melanoma cells show organized neural differentiation forming tumor-vascular complexes. The present study explores the sequence of neurogenesis from aurophilic radial glial like cells in relation to angiogenesis, utilizing the tumor-vascular-complex (TVC) as a 3D model. Methods:...

The catecholamine, dopamine (DA), is synthesized from 3,4-dihydroxy-L-phenylalanine (L-DOPA) by aromatic L-amino acid decarboxylase (AADC). Dopamine metabolism is regulated by monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT). To measure dopaminergic metabolism, we used microdialysis with radiometric detection to monitor L-[β-(11)C]DOPA metabolites in the extracellular space of th...

l-Dopa, the metabolic precursor of dopamine, is the treatment of choice for the symptomatic relief of the advanced stages of Parkinson's disease. The oral bioavailability of l-dopa, however, is only about 10% to 30%, and less than 1% of the oral dose is estimated to reach the brain unchanged. l-Dopa's physicochemical properties are responsible for its poor bioavailability, short half-life and t...

After demonstration of the decarboxylation of 3,4-dihydroxyphenylalanine (dopa)’ to dopamine (I), the pathway for biosynthesis of norepinephrine shown in Fig. 1 was proposed. Although evidence for this pathway was well established by isot,opic procedures (2, 3), it was not until 1960 that Levin, Levenberg, and Kaufman (4) succeeded in isolating and characterizing the third enzyme in the series,...

UNLABELLED A novel synthetic approach to 6-(18)F-fluoro-3,4-dihydroxy-L-phenylalanine ((18)F-DOPA), involving the nucleophilic substitution of a diaryliodonium salt precursor with non-carrier-added (18)F-fluoride, yielded a product with a specific activity that was 3 orders of magnitude higher than the product of the conventional synthesis method, involving an electrophilic substitution of a tr...

xanthine oxidase plays crucial roles in the production of reactive oxygen species (ros), and uric acid in blood which may lead to gout, one of the oldest known forms of arthritis amongst humans. summer savory (satureja hortensis l.) a medicinal/spice exhibits antioxidant activity, but unknown effects on xanthine oxidase activity. here, for the first time, we examined the effects of s. hortensis...

Haemolymph from late third-instar larvae of the blowflies Calliphora sp. (Karlson & Schweiger, 1961 ; Thomson & Sin, 1970) and Lucilia cuprina (Hackman & Goldberg, 1967) contains phenol oxidase in an inactive or proenzyme form. The anterior end of a late third-instar Sarcophaga larva was pricked with a fine pin and the haemolymph released (approx. 5 0 ~ 1 ) was collected in an ice-cold tube. By...