background:
The protein encoded by this gene is involved in the translocation of cobalamin into the mitochondrion, where it is used in the final steps of adenosylcobalamin synthesis. Adenosylcobalamin is a coenzyme required for the activity of methylmalonyl-CoA mutase. Defects in this gene are a cause of methylmalonic aciduria. [provided by RefSeq, Jul 2008].
Function:
Probable GTPase. May function as chaperone. May be involved in the transport of cobalamin (Cbl) into mitochondria for the final steps of adenosylcobalamin (AdoCbl) synthesis.
Subunit:
Homodimer.
Subcellular Location:
Mitochondrion (Probable).
Tissue Specificity:
Widely expressed. Highest expression is observed in liver and skeletal muscle.
DISEASE:
Defects in MMAA are the cause of methylmalonic aciduria type cblA (MMAA) [MIM:251100]; also known as methylmalonic aciduria type A or vitamin B12-responsive methylmalonicaciduria of cblA complementation type. MMAA is a disorder of methylmalonate and cobalamin metabolism due to defective synthesis of adenosylcobalamin. Inheritance is autosomal recessive.
Similarity:
Belongs to the ArgK family.
Database links:
Entrez Gene: 166785 Human
Entrez Gene: 291939 Rat
Omim: 607481 Human
SwissProt: Q8IVH4 Human
SwissProt: D3ZNY3 Rat
Unigene: 452864 Human
Important Note:
This product as supplied is intended for research use only, not for use in human, therapeutic or diagnostic applications.
甲基丙二酸是甲基丙二酰辅酶A的代谢产物，正常情况下在甲基丙二酰
辅酶A变位酶及维生素B12的作用下转化生成琥珀酸，参与三羧酸循环。甲基丙二酰辅酶A变位酶缺陷或维生素B12代谢障碍导致甲基丙二酸、丙酸、甲基枸橼酸等代谢物异常蓄积，琥珀酸脱氢酶活性下降，线粒体能量合成障碍，引起神经、肝脏、肾脏、骨髓等多脏器损伤。患者脑组织病理分析可见脑萎缩、弥漫性神经胶质细胞增生、星形细胞变性、脑出血、苍白球坏死、丘脑及内囊细胞水肿，均与线粒体功能不良有关。
有病理解剖发现患儿神经胶质细胞反应性增生，深部皮质、小脑颗粒层和胶质细胞发育不良，小脑、脑干、颈髓髓鞘化延迟。另有尸检发现肾脏、肺部血栓性毛细血管病、肝脏弥漫性脂肪变性、骨髓巨幼红细胞增生、严重胃黏膜发育不良伴胃炎。这些表现部分为胎儿时期代谢异常所致损害，部分为出生后有机酸毒性损害所致。
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