The developmental expression and activity of peptidylarginine deiminase inthe mouse

We have measured the expression and activity of peptidylarginine deiminase (PAD, EC 3.5.3.15), the enzyme responsible for converting arginyl residues in proteins to citrullines, ire normal mouse brain homogenate. PAD transcri pts were detected as early as five days and were maximal at one month of ag e. The enzyme protein was also detected at 5 days in an antibody dependent assay and was maximal at 2 months of age, 1 month later than the maximum ex pression of transcripts. As expected, enzyme activity had a similar develop mental profile to that of the enzyme protein. In isolated mouse brain compa ct myelin, the activity was highest at 15 days and fell rapidly to 15% of t his level by 1-2 months. In the 'loose' myelin fraction (heavy myelin) it r emained at the same high level form from 15 days to 8 months. The activity in compact myelin was about 15 times greater than the activity in brain hom ogenate, suggesting much of the enzyme was localized to myelin. (C) 1999 El sevier Science Ireland Ltd. All rights reserved.