Abstract
Summary: An 18-year-old mentally and physically retarded male with periodic hyperammonemia is described. Levels of lysine and citrulline in his serum and those of blood ammonia were elevated and daily excretions of homocitrulline in his urine were strikingly high on an ordinary diet. With a decrease in protein intake to 1.5 g/kg body weight/day, only urinary homocitrulline excretion remained about 10 times higher than the normal values whereas the other amino acids in his serum and urine appeared to he within the normal range. After an oral load of lysine on a normal protein intake, several abnormal findings were observed. That is, clinically he had episodes of irritability, vomiting, and coma caused by ammonia intoxication. Biochemically, levels of citrulline and arginine in his serum and the urinary homocitrulline excretion rate continued to increase and arginase in the blood cells was markedly depressed. Blood cell arginase, which showed lower activity than that of control subjects, particularly on a normal protein intake, was extremely inhibited by lysine in the in vitro experiment. The citrulline tolerance curve after the load of L-citrulline was found to be normal on a low protein intake. Lysine:NAD-oxidoreductase activity in the liver was near the lower limits of the control values. The activity of argininosuccinate synthetase (ArgSS) was reduced to 22% of the control values. Arginase activity was also reduced.
Speculation: Hyperlysinemia, hypercitrullinemia, and massive homocitrullinuria found in our patient may he due to a partial defect of ArgSS, which has affinity for both citrulline and homocitrulline. We speculate that impairment of ammonia disposal participates in the deficiency of ArgSS as well as arginase.
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Sogawa, H., Oyangi, K. & Nakao, T. Periodic Hyperammonemia, Hyperlysinemia, and Homocitrullinuria Associated with Decreased Argininosuccinate Synthetase and Arginase Activities. Pediatr Res 11, 949–953 (1977). https://doi.org/10.1203/00006450-197709000-00002
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DOI: https://doi.org/10.1203/00006450-197709000-00002
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