SUBCELLULAR AND DEVELOPMENTAL STUDIES OF THE TYROSYL PROTEIN SULFOTRANSFERASE IN RAT-BRAIN

1. Tyrosyl protein sulfotransferase (TPS) activity in the newborn and mature rat brain was studied using the cholecystokinin derivative tylo xycarbonyl-Asp-Tyr-Met-Gly-Trp-Met-Asp-PheNH2, BocCCK-8(ns), as the pe ptide substrate. 2. TPS activity was enriched 4 times in the microsoma l and synaptic vesicular enriched fractions of rat cerebral cortex. 3. CCK-8 content, in the subcellular fractions and the peptide sulfation activity distribution was in accord with the hypothesis that tyrosyl protein sulfotransferase plays a key role in the maturation process of bioactive CCK. 4. TPS activity measured in membranes from newborn bra in was 2.5 times higher than the activity observed in the mature brain membranes with a V(max) = 0.83 +/- 0.05 and 0.31 +/- 0.02 respectivel y. The apparent K(M) for the sulfate donor, 3'-phosphoadenosine 5'-pho sphosulfate (PAPS), was similar, 94 +/- 4 nM and 90 +/- 6 nM and the K (M) for the peptide substrate, BocCCK-8(ns), was 234 +/- 16 muM and 16 0 +/- 12 muM in the newborn and adult brain membranes respectively. 5. TPS activity reached normal mature values within 20 days of age. 6. T hese data support the idea that tyrosyl protein sulfation is an import ant process in the secretion mechanism and in the CCK maturation.