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O Kwon

Publications and source records attributed to O Kwon.

44 records · Page 3Linked to original sources
PubMed1991

Catalytic and regulatory properties of native and chymotrypsin-treated pyridoxine-5-phosphate oxidase.

Brain pyridoxine-5-P oxidase is activated by the tryptophan metabolites 3-hydroxyanthranilate and 3-hydroxykynurenine. 3-Hydroxyanthranilate at concentrations of 0.03 mM relieves the inhibition elicited by accumulation of the substrate pyridoxine-5-P (Ki = 60 microM). The results of fluorometric measurements indicate that four molecules of 3-hydroxyanthranilate bind to the dimeric enzyme (56 kDa) with an association constant of 5.5 x 10(4) M-1. Differential spectral measurements failed to detect any direct interaction between the cofactor FMN and the effector 3-hydroxyanthranilate. These results are consistent with the hypothesis that the effector molecules bind to sites of the dimeric protein distinct from the cofactor site. Limited chymotrypsin digestion of pyridoxine-5-P oxidase yields catalytically active species that are no longer susceptible to activation by 3-hydroxykynurenine. A polypeptide of 16 kDa containing FMN and endowed with full catalytic activity was isolated by ion-exchange chromatography. It is postulated that the structural domain associated with catalytic activity composes approximately one-half of the molecular mass of pyridoxine-5-P oxidase (28 kDa), whereas the remaining portion of the macromolecule contains regulatory binding sites.

Animals↗
PubMed1990

Absence of diuresis during a 7-day saturation dive at 2.5 ATA N2-O2.

Three male divers were studied for 2 days during each of the predive and postdive 1 ATA air control periods and for 7 days at 2.5 ATA (2.3 ATA N2 and 0.2 ATA O2). The chamber temperature was always maintained at a comfort level. Average urine flow remained at 1500 ml.day-1 during both predive and 2.5 ATA periods; urine osmolality also remained constant at around 700 mOSM/kg. On the other hand, daily excretion of Na increased significantly from 139 mEq during the predive period to 178 mEq at 2.5 ATA (P less than 0.05) but returned to the predive level during the postdive period. In contrast, daily K excretion decreased progressively with a significant decrease during the postdive period (P less than 0.05). Plasma osmolality, Na, and K remained unchanged, whereas a 6% reduction of total protein concentration at 2.5 ATA (P less than 0.05) was observed. A quantitatively similar decrease (8%) was observed for hematocrit during the 2.5 ATA period, which did not recover at postdive. These changes were accompanied by a significant increase in urinary excretion of antidiuretic hormone (P less than 0.05) and by decreases in both plasma renin and aldosterone (P less than 0.05) level and urinary excretion of aldosterone (P less than 0.05). Plasma atrial natriuretic factor remained unchanged throughout the entire dive period.

Adult↗
PubMed1989

Size selected mRNA induces expression of P-aminohippurate transport in Xenopus oocytes.

Xenopus oocytes were injected with size-fractionated mRNA isolated from the renal cortex of rabbit kidney and after 4 days incubation, PAH uptake in oocytes injected with mRNA (0.7-1.3 kb) was 8 to 45 fold that of the water injected controls. The oocyte to medium ratio of accumulated PAH was 1.95. The Km and Vmax for transport were 333 microM and 66.6 nmoles.oocyte-1.min-1, respectively. This Km is similar to that reported for PAH transport in intact kidneys and slices. The uptake of PAH was unaffected by the absence of Na+ or the presence of probenecid. Expression of the transport represents the first step in an effort to clone and identify the gene for PAH transport.

Aminohippuric Acids↗
PubMed1988

Sulfate homeostasis. I. Effect of salicylic acid and its metabolites on inorganic sulfate in rats.

Homeostasis of inorganic sulfate, a physiologic anion necessary for both detoxification and biosynthetic reactions, involves predominantly capacity-limited renal clearance mechanisms. The objective of this investigation was to examine the effect of salicylic acid (SA) and its major metabolites, salicyluric acid and salicyl phenolic glucuronide, on the serum concentrations and renal clearance of inorganic sulfate in rats. Animals were studied using a crossover design in which they received a bolus i.v. injection (75 mg/kg) and infusion (approximately 0.26 mg/min/kg) of SA or the same volume of saline (the vehicle). Blood samples were collected at 2, 3 and 4 hr after administration and urine between 2 and 4 hr. The renal clearance of sulfate and creatinine were examined at mean steady-state SA serum concentrations of 249 micrograms/ml. Although no changes in the serum concentrations and renal clearance of creatinine were observed, the renal clearance of inorganic sulfate was increased significantly (2.13 +/- 0.74 vs. 1.09 +/- 0.54 ml/min/kg in controls, mean +/- S.D., n = 7) and its serum concentration decreased (0.55 +/- 0.12 vs. 1.04 +/- 0.23 mM in controls). These changes were not due to alterations in uric acid concentrations as uric acid serum concentrations and renal clearance were unchanged when examined at similar steady-state SA serum concentrations in a subsequent study. The effects on sulfate disposition also were probably not due to the major metabolites of SA: no changes in the serum concentrations or renal clearance of sulfate were observed at mean steady-state concentrations of 52 micrograms/ml of salicyluric acid or 73.7 micrograms/ml of salicyl phenolic glucuronide after their direct administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗