Young Sarah, Struys Eduard, Wood Tim
Duke University Medical Center, Research Triangle Park, North Carolina, USA.
Curr Protoc Hum Genet. 2007 Jul;Chapter 17:Unit 17.3. doi: 10.1002/0471142905.hg1703s54.
Inherited defects in creatine biosynthesis and cellular uptake are neurometabolic disorders characterized by seizures, developmental delay, mental retardation, autistic-like behavior, and creatine deficiency in the brain. Metabolic screening of these disorders is possible using analytical techniques that quantify creatine and its precursor guanidinoacetate in urine, plasma, or cerebrospinal fluid (CSF). Elevated creatine in urine is suggestive of a deficiency of the X-linked creatine transporter, SLC6A8. Decreased or elevated levels of guanidinoacetate in urine, plasma, or CSF suggest deficiencies of the creatine biosynthetic enzymes, arginine:glycine amidinotransferase (AGAT) or guanidinoacetate methyltransferase (GAMT), respectively. This unit describes three stable isotope dilution-mass spectrometric methods for analyzing creatine and guanidinoacetate. Gas chromatography/mass spectrometry with negative-ion chemical ionization is a highly sensitive technique, suitable for detection of low analyte levels resulting from AGAT deficiency and in CSF. The two liquid chromatography-tandem mass spectrometric approaches are amenable to high-throughput screening and have simple sample preparation requirements.
肌酸生物合成和细胞摄取的遗传性缺陷是神经代谢紊乱，其特征为癫痫发作、发育迟缓、智力迟钝、自闭症样行为以及大脑中的肌酸缺乏。使用能够定量尿液、血浆或脑脊液（CSF）中肌酸及其前体胍基乙酸的分析技术，可以对这些疾病进行代谢筛查。尿液中肌酸升高提示X连锁肌酸转运体SLC6A8缺乏。尿液、血浆或脑脊液中胍基乙酸水平降低或升高分别提示肌酸生物合成酶精氨酸：甘氨酸脒基转移酶（AGAT）或胍基乙酸甲基转移酶（GAMT）缺乏。本单元介绍了三种用于分析肌酸和胍基乙酸的稳定同位素稀释-质谱法。具有负离子化学电离的气相色谱/质谱法是一种高度灵敏的技术，适用于检测由AGAT缺乏导致的低分析物水平以及脑脊液中的分析物。两种液相色谱-串联质谱方法适用于高通量筛查，且样品制备要求简单。
