DISTRIBUTION OF BRANCH POINT PRENYLTRANSFERASES IN REGIONS OF BOVINE BRAIN

Bovine brains contain large amounts of isoprenoid compounds and the en zymes involved in their biosynthesis were investigated. Ten different regions were dissected from fresh bovine brains and, in addition, frac tions from cerebellum, spinal cord, and hypophysis were obtained, The cholesterol concentration was found to be similar to 8 mg/g in the cor tex regions and three times higher in the pens, medulla oblongata, and white matter, Dolichol concentration varied between 8 and 40 mu g/g i n the different tissues, and ubiquinone was found at a lower level, wh ich varied between 3 and 25 mu g/g, Farnesylpyrophosphate synthase act ivity in cytosolic fractions from various regions exhibited only a two fold variation, whereas geranylgeranyl pyrophosphate synthase displaye d larger differences, being particularly rich in the pens, medulla obl ongata, white matter, and spinal cord. Squalene synthase activity was lowest in the thalamus and threefold higher in the pens, Determination of specific activity based on cholesterol content revealed that enzym e activities in various regions are not related to the actual lipid am ount present. Both cis- and trans-prenyltransferases exhibited similar ities in their regional distribution showing up to 20-fold differences in activity. Thus, it appears that the mevalonate pathway lipids and the various branch point enzymes involved in their syntheses vary grea tly in different brain regions and are subjected to separate regulatio n.