Heterogeneity in genetic control of phenylalanine metabolism in man.

Abstract

A HEPARINIZED blood sample was obtained from the antecubital vein just before the noon meal from twenty-five unrelated normal adult subjects and eighteen parents of eleven phenylketonurie probands. After deproteinization (plasma: picric acid, 0.427 N, 1 : 5 v/v). centrifugation and removal of the picric acid from the supernatant on ‘Dowex-2 × 8’ resin, a volume of the filtrate equivalent to 0.416 ml. of original plasma was applied to a 22 cm column of spherical resin of 13µ particle size and 7.5 per cent cross-linkage (Beckman–Spinco spherical resin, PA-35). Elution, at 50 ml./h, was performed on a modified Beckman–Spinco amino-acid analyser at 65° C with pH 4.25 sodium citrate buffer, 0.2 N, with respect to sodium1,2. This procedure elutes tyrosine and phenylalanine as two discrete peaks at 51 and 55 min, respectively. The mean error of the method is ±2.1 per cent and ±1.7 per cent for tyrosine and phenylalanine, respectively; the recoveries are 100–103 per cent and 97–101 per cent, respectively, for the concentrations 0.01 to 0.20 µmoles (ref. 2).