<prompt> Answer this question truthfullyWhat is the effect of Carbamoyl phosphate synthetase I deficiency on BUN levels?  <response>: <reason> Carbamoyl phosphate synthetase I deficiency is a genetic disorder that affects the urea cycle, leading to the buildup of toxic levels of ammonia in the blood. BUN blood urea nitrogen is a measure of the amount of nitrogen in the blood that comes from the breakdown of urea. In Carbamoyl phosphate synthetase I deficiency, the urea cycle is disrupted, leading to decreased production of urea and therefore decreased BUN levels. This can be used as a diagnostic marker for this condition. 