Two of the proteins were lower in PBMCs from ME/CFS patients than controls; MCCC2 (subunit of 3-methylcrotonoyl-CoA carboxylase) involved in breaking down the amino acid leucine to acetyl-CoA, and SUCLG1, a subunit of the citric acid cycle enzyme, succinate coenzyme A ligase, which catalyses the conversion of succinyl-CoA to succinate. Here, MCCC2 is linked to myalgic encephalomeyelitis/chronic fatigue syndrome.