Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “urate”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 55 records · Page 3Linked to original sources
PubMed1976

Urate kinetics in hypoxanthine-guanine phosphoribosyltransferase deficiency: their significance for the understanding of gout.

Urate production (miscible urate pool and turnover, daily production, glycine incorporation into urate) and urate excretion (24 hour urinary urate excretion on a purine free diet, renal clearances of urate and creatinine, per cent renal excretion of labelled urate, extra-renal elimination of urate) were measured in members of five families who demonstrated varying degrees of deficiency of the X-linked condition hypoxanthine-guanine phosphoribosyltransferase (HGPRT) deficiency. The hemizygous males, all of whom eventually developed symptoms, showed consistent overproduction of urate with a renal excretion of urate that varied from moderately to considerably increased. The nine heterozygotes, of whom seven were asymptomatic, also showed abnormalities of urate production, although all but two had normal serum urate concentrations. The one heterozygote who had developed gouty arthritis had the lowest renal excretory capacity for urate, whereas the one heterozygote who had developed an episode of renal colic had the highest urate clearance. In the heterozygotes with normal serum urate concentrations, the increase urate production was balanced by the renal excretion of urate. This demonstrates the importance of the relation between urate. This demonstrates the importance of the relation-between urate production and urate excretion in determining the clinical expression of abnormal urate metabolism.

Adolescent↗
PubMed1986

Characteristics of renal p-aminohippurate and urate excretion in rabbits.

Urate and p-aminohippurate (PAH) excretion was studied in New Zealand white rabbits to determine the extent to which the renal tubular handling of these organic anions by intact kidneys paralleled observations made in single isolated perfused tubules in vitro. At low plasma concentrations (less than 60 mumol/L) net reabsorption of urate was observed in the majority of animals; as plasma urate concentration was increased by infusing lithium urate, net urate secretion was demonstrated, the fractional excretion of urate (FE urate) reaching 270%, and net urate secretion (filtered urate minus urinary concentration of urate times volume flow rate) 1.8 mumol/min at mean plasma urate levels 200 and 310 mumol/L. A maximal urate secretion rate was not demonstrated. Probenecid (250 mumol/kg) reduced FE urate to 27%, thereby revealing concealed reabsorption despite high plasma urate levels. By contrast, net secretion of PAH at all plasma levels was achieved by infusing NaPAH. The highest secretory rate was 38.6 mumol/min at plasma PAH levels between 1000 and 1750 mumol/L. Probenecid reduced fractional excretion of PAH (FEPAH) from 796% to 265%, no evidence of PAH reabsorption being found after inhibition of secretion with probenecid. At comparable plasma levels (220 mumol/L), net PAH secretion exceeded net urate secretion (reflected by the decrement in urate and PAH excretion caused by probenecid) by a factor of 5.3:1. These experiments indicate that urate and PAH are filtered and secreted by the rabbit kidney; however, only urate is significantly reabsorbed over the range of plasma organic anion levels examined. The configuration of the relation between plasma levels and net secretion rates and the greater secretory rate for PAH for urate in the living rabbit are consonant with the characteristics of PAH and urate transport determined previously in studies of isolated perfused proximal tubules.

Aminohippuric Acids↗
PubMed1997

Kinetic mechanism and cofactor content of soybean root nodule urate oxidase.

The kinetic mechanism of urate oxidase isolated from soybean root nodules has been determined by initial velocity kinetic studies monitoring oxygen uptake, in order to avoid potential artifacts in the spectrophotometric assay which arise from absorbance due to unidentified products of the enzymatic reaction. Urate and O2 bind to the enzyme sequentially; xanthine is a competitive inhibitor versus urate and a noncompetitive inhibitor versus O2, which suggests that urate binds to the enzyme before O2. This kinetic mechanism was confirmed by an 18O isotope-trapping experiment, which demonstrated that O2 does not bind productively to the enzyme in the absence of urate. The pH dependence of V and (V/K)urate reveal the presence of an ionizable residue on the enzyme with a pK of approximately 6.2, which must be unprotonated for the catalytic reaction to occur. The (V/K)O2 profile is pH independent; these data are accomodated by a model in which a unimolecular step intervenes between the binding of urate and O2. The pKi profile for 9-methylurate, a competitive inhibitor versus urate, is pH independent, confirming that the protonation state of the ionizable residue is not important for binding. The pKi profile for xanthine defines a pK of 7.4, which demonstrates that the monoanion of xanthine binds to the enzyme; by analogy, the monoanion of urate is predicted to be the substrate. The four isomeric N-methylurates were examined as potential inhibitors of urate oxidase. Only 9-methylurate showed significant inhibition suggesting that ionization at N9 of urate is not required for binding; it is proposed that the N3-deprotonated urate monoanion is the species which binds to urate oxidase. The gene encoding urate oxidase was cloned from soybeans and expressed in Escherichia coli. The metal content of the recombinant enzyme was examined by inductively coupled argon plasma emission spectroscopy, and only trace quantities of copper were found. The molecular mass of the protein was determined by MALDI-TOF mass spectrometry and found to be 35,059.8 Da. The calculated molecular mass of urate oxidase is 35,052 Da; therefore, these data suggest that there is no covalently bound cofactor in urate oxidase.

Cloning, Molecular↗