Enables SUMO transferase activity. Acts upstream of or within positive regulation of glucokinase activity and regulation of gluconeogenesis. Located in mitochondrion. Is expressed in several structures, including alimentary system; early conceptus; hemolymphoid system; nervous system; and reproductive system. Human ortholog(s) of this gene implicated in brain disease and inflammatory myofibroblastic tumor. Orthologous to several human genes including RANBP2 (RAN binding protein 2). [provided by Alliance of Genome Resources, Apr 2022]