Phenylalanine hydroxylase from human kidney.

Abstract

In this report the presence, and level, of phenylalanine hydroxylase in the cortex of human kidney is established. The average activity found in 15 surgically removed kidneys was 47.2 plus or minus 11.2 mU/g wet weight of tissue. The average value, determined under the same experimental conditions, for two human liver biopsies was 217 mU/g tissue. Of five autopsy livers obtained 2.5-4 h postmortem, four contained no activity, and only 1-2 percent of normal was found in the fifth. Autopsy kidneys were similarly inactive. The presence of a highly active degradative enzyme could not be demonstrated in autopsy liver homogenates; it was established that the lack of activity was not due to an inhibitory component. A possible interpretation of this phenomenon is discussed. According to work published elsewhere [13] the kidney and liver enzymes appear to be similar. Thus, surgically removed kidneys provide an alternative source of human phenylalanine hydroxylase which can be used to study phenylketonuria.