Kang E S, Seyer J, Todd T A, Herrera C
Hum Genet. 1983;64(1):80-5. doi: 10.1007/BF00289484.
A retarded child with hypersarcosinemia and his family were studied by loading tests to determine the probable site of his defect. On the basis of his response to folate treatment, a partially-reversible defect in the formation of activated formaldehyde in the reaction catalyzed by sarcosine dehydrogenase was considered to be the most likely site. During a glycine loading test, sarcosine levels in the plasma and urine increased, indicating that the direct transmethylation of glycine to sarcosine could occur in this patient. The father of the proband tolerated a load of sarcosine poorly, resembling the proband in his plasma sarcosine levels. No evidence that glycine could be transmethylated to sarcosine was found in the father, despite the fact that his peak glycine level was four times higher than the proband's. These findings provide indirect evidence that sarcosine formation may be affected by two additional components besides the apo moiety of sarcosine dehydrogenase, the availability of tetrahydrofolic acid as a one carbon unit carrier and the integrity of the transmethylase which catalyzes the direct transmethylation of glycine to sarcosine.
对一名患有高肌氨酸血症的智力发育迟缓儿童及其家人进行了负荷试验，以确定其缺陷可能所在的位置。根据他对叶酸治疗的反应，肌氨酸脱氢酶催化的反应中活性甲醛形成的部分可逆缺陷被认为是最可能的位置。在甘氨酸负荷试验期间，血浆和尿液中的肌氨酸水平升高，表明该患者中甘氨酸可直接甲基化生成肌氨酸。先证者的父亲对肌氨酸负荷的耐受性较差，其血浆肌氨酸水平与先证者相似。尽管父亲的甘氨酸峰值水平比先证者高四倍，但未发现父亲体内甘氨酸可甲基化生成肌氨酸的证据。这些发现提供了间接证据，表明除了肌氨酸脱氢酶的脱辅基部分外，肌氨酸的形成可能还受另外两个因素影响，即作为一碳单位载体的四氢叶酸的可用性以及催化甘氨酸直接甲基化生成肌氨酸的甲基转移酶的完整性。
