苯丙氨酸和酪氨酸的代谢缺陷,可引起苯丙酮酸尿症、白化病、尿黑酸症,酪氨酸血症等先天性代谢缺陷疾病。苯丙酮酸尿症即苯丙氨酸羟化酶缺乏,使苯丙氨酸不能转变为酪氨酸,而大量转变为苯丙酮酸并由尿中排出。患儿血清中苯丙氨酸量增高而酪氨酸量降低。由于苯丙酮酸的堆积对神经有毒性,对神经系统发育有抑制作用,所以患儿智力发育出现障碍。如患儿出生后能早期诊断并控制膳食中苯丙氨酸的摄入量,患儿的预后较好。如不予治 Phenylalanine and tyrosine metabolic defects, can cause phenylketonuria, albinism, alzheimer’s disease, tyrosinemia and other congenital metabolic defects. Phenylpyruvic aciduria, a deficiency of phenylalanine hydroxylase, prevents phenylalanine from being converted to tyrosine and a substantial conversion to phenylpyruvate and excretion from the urine. Children with serum phenylalanine increased the amount of tyrosine decreased. Due to the accumulation of phenylpyruvate nerve toxicity, inhibition of the development of the nervous system, so children with mental retardation. Such as children born early diagnosis and control of dietary phenylalanine intake, children with better prognosis. If not treated