Iron-sulfur protein (IP) subunit of the succinate dehydrogenase complex (mitochondrial respiratory chain complex II), responsible for transferring electrons from succinate to ubiquinone (coenzyme Q) (PubMed:26925370, PubMed:27604842). SDH also oxidizes malate to the non-canonical enol form of oxaloacetate, enol- oxaloacetate (By similarity). Enol-oxaloacetate, which is a potent inhibitor of the succinate dehydrogenase activity, is further isomerized into keto-oxaloacetate (By similarity). {ECO:0000250|UniProtKB:Q3T189, ECO:0000269|PubMed:26925370, ECO:0000269|PubMed:27604842}. This is the function of ENSG00000117118 (SDHB, succinate dehydrogenase complex iron sulfur subunit B).