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. Defects in MMAA are the cause of methylmalonic aciduria type cblA (MMAA); 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. Belongs to the ArgK family. Note: This description may include information from UniProtKB.