Biotinidase catalyzes debiotinylation of histones

Background Posttranslational modifications of histones play important roles in processes such as regulation of gene expression and DNA repair. Recently, evidence has been provided that histones in human cells are modified by covalent attachment of biotin. Aim of the study To determine whether the reverse process (debiotinylation of histones) occurs in biological samples and whether debiotinylation is an enzyme-mediated process; and to characterize the enzyme that mediates debiotinylation of histories. Methods Plasma and lymphocytes from healthy adults and a biotinidase-deficient patient were used as sources of debiotinylating enzymes. Debiotinylation of histones by plasma and lymphocyte proteins was measured using a colorimetric 96-well plate assay. Results Histories were debiotinylated rapidly if incubated with human plasma or lysates of lymphocytes. The following observations are consistent with the hypothesis that debiotinylation is an enzyme-mediated process: (i) Hydrolysis was slower at 4 degreesC compared to 37 degreesC; (ii) debiotinylating activity was destroyed when biological samples were heated at 90 degreesC for 30 min preceding incubation with biotinylated histories; and (iii) rates of debiotinylation were pH dependent. Rates of histone debiotinylation were significantly decreased in biotinidase-deficient samples. Conclusion Debiotinylation of histories in human samples is an enzyme-mediated process that is at least partly catalyzed by biotinidase.