[An enzymatic determination of serum citrate with citrate lyase]

A method for the enzymatic determination of the serum citrate using citrate lyase is described. The optimum pH was equal to or higher than 8.6. Prior to the determination of the serum citrate, the samples were deproteinized with perchloric acid. After the precipitation of the proteins, potassium hydroxide was added under an ice-cooling condition in order to neutralize the solution. The recovery rates of the citrate added to serum ranged from 92% to 108%, and the coefficient of variation of triplicate assay was 4.2%. The mean serum value of 17 healthy subjects was 1.57 mg/dl, with a range of 1.03-2.03 mg/dl. In seven healthy subjects, 3 g of sodium-potassium citrate was administered orally and the serum citrate was measured 0, 15, 30, 45, 60, and 120 min later. The serum citrate was significantly increased in the periods between 15 and 60 min.