Enables isocitrate dehydrogenase (NAD+) activity. Involved in several processes, including NADH metabolic process; carboxylic acid metabolic process; and tricarboxylic acid cycle. Predicted to be located in nucleolus. Predicted to be part of mitochondrial isocitrate dehydrogenase complex (NAD+). Predicted to be active in mitochondrion. Orthologous to human IDH3G (isocitrate dehydrogenase (NAD(+)) 3 non-catalytic subunit gamma). [provided by Alliance of Genome Resources, Apr 2022]