Changes in the composition of salivary amino acids, proteins and enzymes in children with phenylketonuria.

Since children with phenylketonuria have a low incidence of caries, the aim of this study was to examine the changes occuring in the airninoacid and protein composition as well as in the composition of salivary enzymes, which might serve as biochemical indicators, representing the factors of predisposition to the development of caries. For this purpose, the analysis was carried out in the native, unstimulated, mixed salivary specimens taken from the sublingual region of children with late diagnosis of RKU (n — 16), those with early diagnosis of the dis­ order by means of a systematic diagnostic screeniig program for PKU using Guthrie’s test (n — 7), and a control group of children free of any disturban­ ces of the a mi no-acid metabolism (n — 44). lA method of qualitative chromatography on silica gel was used for separation of aminoacids, while the proportions of each individual aminoacid were determined by a densitometer. The content of total salivary pro­ teins was assessed by the method of Lowry, and the con cent ration of lysozyme by the method of Prockop. Differences in particular proportions o aminoacids, and an increase in the total protein value as well as in the lysozyme activity, could be taken as the factors of predisposition or resistance to caries.