Peptidylarginine deiminase activity in postmortem white matter of patients with multiple sclerosis

The myelin sheath in multiple sclerosis (MS) appears to contain a higher proportion of the citrullinated isoform of myelin basic protein MBP-C8. In vitro, MBP-associated arginine is deiminated to citrulline by the enzyme peptidylarginine deiminase (PAD). We investigated PAD activity in white matter from postmortem human brain samples by measuring the formation of citrulline from benzoylarginine ethyl esther. PAD activity in MS white matter was not different from that in controls. in neonates, in whom MBP is exclusively of the C8 type, white matter PAD activity was not different from that in adults. Our results suggest that in human brain either PAD plays no role in the formation of MBP-C8, or there may be a better accessibility of MBP in myelin in neonates and MS to the enzyme. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.