Fluorometry of Citrate in Serum, with Use of Citrate (pro-3S)-Lyase

Abstract

We describe a procedure for enzymatic assay of citrate in human serum. The citrate is degraded to acetate and oxaloacetate with citrate oxaloacetate-lyase (pro-3S-CH2 · COO- → acetate) (EC 4.1.3.6). Some oxaloacetate loses CO2 to form pyruvate. Addition of malate and lactate dehydrogenases (EC 1.1.1.37 and 1.1.1.27) permits determination of the oxaloacetate and pyruvate generated, and thus of the citrate concentration. The decrease in NADH concentration is measured fluorometrically. Results obtained for 30 consecutive human sera by this procedure were compared to the procedure in which the citrate is converted to pentabromoacetone. There was no statistically significant difference in values obtained by the two procedures. The range of values (mean ± 2 SD) found for sera from 25 blood donors by this procedure was 12.8-27.2 mg/liter (mean, 19.0 mg/ liter). Serum citrate as measured by both procedures during a glucose tolerance test was decreased from initial values under the influence of administered glucose (and endogenous insulin). Insulin concentrations were also measured during these glucose-tolerance tests. Citrate concentrations remain subnormal after the glucose and insulin concentrations return to their initial values. This accords with published reports.

Urinary analysis of nephrolithiasis markers

“…The traditional enzymatic method for the determilated by calcium oxalate crystals, and this protein, nation of citrate uses citrate lyase, malate dehydrowhich is excreted from the tubular cells, may inhibit genase, lactate dehydrogenase and NADH [60] and it calcium oxalate crystals' aggregation and attachment is monitored spectrophotometrically or fluorimetrito cells. The fibronectin content was measured with cally [61][62][63]. the sandwich enzyme-linked immunosorbent assay Petrarulo et al have proposed a new method for method using a fibronectin kit.…”

Antigenic Homology of the Inducible Ferric Citrate Receptor (FecA) of Coliform Bacteria Isolated from Herds with Naturally Occurring Bovine Intramammary Infections

“…As a novel signal transduction model, the ferric citrate iron uptake system has been thoroughly investigated over the past 18 years (reviewed in references 2 and 3). However, no information exists concerning the role of the ferric citrate iron uptake system as a pathogenic mechanism in bacteria, because the concentration of citrate in the vertebrate host generally is too low to induce the bacterial ferric citrate system (29). However, bovine milk appears to provide an ideal environment for induction of the ferric citrate iron transport system.…”

Citrate metabolism by human platelets

“…Citrate is needed as anticoagulant in storage media and since it is also a normal metabolic intermediate (found in whole blood at Ϸ 0 . 1 mM, Tomisek et al, 1975), it seemed possible that it could be used by platelets and other blood cells. However, it is not known whether there is a citrate receptor or transport mechanism in platelets which would allow exogenous citrate to be metabolized.…”