[Determination of kynureninase activity in oligophrenic children with hereditary taint, before and after vitamin B6 treatment].

Kynureninase activity assay in oligophrenic children with hereditary taint, before and after treatment with vitamin B6. The hepatic kynureninase activity was assayed in 25 oligophrenic children with hereditary taint, and having a positive tryptophan load test. Eight cases (32%) showed an enzyme activity below the 2-s limit; in two cases, the pathologic enzyme activity could be almost normalized by addition of higher P-5-P concentrations. In a second set of studies, eight children with an abnormally low kynureninase activity were re-examined following a 3-week treatment with vitamin B6. The enormous in-vivo-activation of kynureninase reached in these studies lends support to the assumption of a vitamin-B6-dependent "inborn error of metabolism" in the tryptophan-kynurenin pathway in some of the investigated oligophrenic children with hereditary taint.