Citrate in urine determined with a new citrate lyase method

Abstract

An enzyme-spectrophotometric method to determine citrate in biological fluids is proposed, based on citrate lyase-catalyzed and phenylhydrazine reactions. The enzyme converts citrate into oxaloacetate, which, in the presence of phenylhydrazine, is transformed into the corresponding phenylhydrazone. The ultraviolet-absorbing product is determined by absorbance measurement at 330 nm. The method is more precise and twice as sensitive as the traditional citrate lyase method and, because it does not require the use of additional enzymes and coenzymes, is cheaper and simpler. Mean analytical recovery of citrate averaged 100.7% +/- 2.2%, imprecision (CV) of the assay for citrate at 0.96 mmol/L (urine) was 2.0%, and the lower limit of quantification was 0.08 mmol/L. Results correlated well with those by both ion-chromatographic and traditional citrate lyase methods.

Effect of nitrogen source on the solubilization of different inorganic phosphates by an isolate of Penicillium rugulosum and two UV-induced mutants

“…The elution was performed in 22 min, with a gradient that started with 2 mM and ended with 32.45 mM NaOH containing 18% methanol. Culture ¢ltrate samples and standard controls of citric and gluconic acids were incubated with citrate lyase [20] or gluconate kinase and ATP [21] in order to con¢rm the presence of citric and gluconic acids.…”

Endogenous and exogenous citrate transport and release in prostatic preparations: semi-polarized two-dimensional cultures of human PNT2-C2 cells and isolated tubules and segments of rat prostate

“…The pH of the solution was adjusted to 7.2 with 1M NaOH or 1 mM HCl. Patch pipettes were filled with a solution containing (in mM): NaCl (5), KCl (145), MgCl 2 (2), CaCl 2 (1), HEPES (10), and EGTA (11). This was adjusted to pH 7.4 with 1M KOH and the resulting electrodes had resistances of 5-15 MO.…”

“…The amount of citrate released from segments of rat prostate was measured by the spectrophotometric ''citrate lyase method'' described earlier [8,11]. Prostate segments were obtained as described previously [13,14].…”

“…In order to bring the research closer to the in vivo situation, we also used segments and tubules isolated from the rat prostate. Citrate release was measured using two different techniques, enzymespectrophotometry [11] and NADH fluorescence [12].…”

Determination of oxalate and citrate in urine by capillary electrophoresis using solid‐phase extraction and capacitively coupled contactless conductivity based on an improved mini‐cell

“…Article Related Abbreviations: C 4 D, capacitively coupled contactless conductivity detection; CTAB, hexadecyl trimethyl ammonium bromide; DAD, diode-array detector; HAc, acetic acid; His, L-histidine; MeOH, methanol; MES, 2-(N-Morpholino) ethanesulfonic acid To date, many methods have been recommended for the determination of oxalate and citrate in clinical laboratory analyses. They include HPLC-UV [3,4], GC-MS [5], ion chromatography with suppressed conductivity detection [6][7][8], enzymatic techniques [9][10][11][12], etc. However, most of these methods are either time-consuming or require expensive and sophisticated instruments, well controlled experimental conditions, and sample pretreatment.…”