Enzymatic sulphation of some galactose- containing sphingolipids in developing rat brain

Lipids of nervous tissue: composition and metabolism

As indicated in the Introduction, the many significant developments in the recent past in our knowledge of the lipids of the nervous system have been collated in this article. That there is a sustained interest in this field is evident from the rather long bibliography which is itself selective. Obviously, it is not possible to summarize a review in which the chemistry, distribution and metabolism of a great variety of lipids have been discussed. However, from the progress of research, some general conclusions may be drawn. The period of discovery of new lipids in the nervous system appears to be over. All the major lipid components have been discovered and a great deal is now known about their structure and metabolism. Analytical data on the lipid composition of the CNS are available for a number of species and such data on the major areas of the brain are also at hand but information on the various subregions is meagre. Such investigations may yet provide clues to the role of lipids in brain function. Compared to CNS, information on PNS is less adequate. Further research on PNS would be worthwhile as it is amenable for experimental manipulation and complex mechanisms such as myelination can be investigated in this tissue. There are reports correlating lipid constituents with the increased complexity in the organization of the nervous system during evolution. This line of investigation may prove useful. The basic aim of research on the lipids of the nervous tissue is to unravel their functional significance. Most of the hydrophobic moieties of the nervous tissue lipids are comprised of very long chain, highly unsaturated and in some cases hydroxylated residues, and recent studies have shown that each lipid class contains characteristic molecular species. Their contribution to the properties of neural membranes such as excitability remains to be elucidated. Similarly, a large proportion of the phospholipid molecules in the myelin membrane are ethanolamine plasmalogens and their importance in this membrane is not known. It is firmly established that phosphatidylinositol and possibly polyphosphoinositides are involved with events at the synapse during impulse propagation, but their precise role in molecular terms is not clear. Gangliosides, with their structural complexity and amphipathic nature, have been implicated in a number of biological events which include cellular recognition and acting as adjuncts at receptor sites. More recently, growth promoting and neuritogenic functions have been ascribed to gangliosides. These interesting properties of gangliosides wIll undoubtedly attract greater attention in the future.(ABSTRACT TRUNCATED AT 400 WORDS)

Enzymatic sulfation of glycosphingolipids in rat parotid salivary glands

The results of this study demonstrate that sulfatoglycosphingolipids of rat parotid salivary glands consist of galactosylceramide and lactosylceramide sulfates. The enzyme activity which catalyzes the formation of these compounds in vitro via transfer of sulfate from 3'-phosphoadenosine-5'-phosphosulfate to galactosyl- and lactosylceramide is located in the microsomal fraction of parotid glands. This sulfotransferase exhibits its optimum activity at pH 6.8 and requires the presence of Triton X-100, Mg2+, and F1-.

Cerebroside sulfotransferase in rat gastric mucosa

1. Cerebroside sulfotransferase activity was demonstrated in rat gastric mucosa. This enzyme preparation catalyzes the transfer of sulfate group from 3'-phosphoadenosine-5'-phosphosulfate to added cerebroside and lactosylceramide. 2. Psychosine also serves as an acceptor for sulfate group. 3. Both hydroxy-fatty acid and non-hydroxy-fatty acid containing cerebrosides are equally sulfated. However, this enzyme is inactive toward glucosylceramide. 4. The optimum pH is around 6.0. The reaction is stimulated by the addition of 0.4-0.9% of Triton X-100. 5. The presence of 2-4 mM ATP moderately stimulates the reaction, but is inhibitory when the concentration exceeds 6 mM. 6. EDTA has no effect. 7. Both Mg2+ and Ca2+ stimulate at lower concentrations (less than 16 mM), but inhibit at higher concentrations (greater than 20 mM). Mn2+, however, is a strong inhibitor even at 8 mM concentration. 8. The apparent Km for cerebroside is 0.04 mM, while that for 3'-phosphoadenosine-5'-phosphosulfate is 0.45 microM.

Genetic control of developmental patterns of cerebral enzyme activities: further differences between C3H and ICR strains of mice

We have investigated developmental changes in activity for five enzymes associated with different cerebral metabolic systems in two separate strains of mice. The enzymes studied were acid beta-galactosidase, arylsulfatase A, cerebroside beta-galactosidase, cerebroside sulfotransferase, and glutamate decarboxylase. The two strains of mice were C3H/SWV and ICR/SWV. We confirm the experiments of Meisler, Paigen, and colleagues showing higher acid beta-galactosidase activity throughout development in C3H mice. In addition we have demonstrated higher arylsulfatase A activity throughout development in C3H mice. The shape of the developmental curve for arylsulfatase A activity in brain in the two strains was similar. There were no differences in developmental changes of activity between the two strains for the other three enzymes studied.

Developmental dissociation of myelin synthesis and "myelin-associated" enzyme activities in the shiverer mouse

Developmental changes in three enzymes associated with myelin lipids were studied in the shiverer mouse, a murine mutant showing a severe deficiency of CNS myelin. Age-related changes in cerebroside sulfotransferase (measured in brain) and arylsulfatase A and cerebroside B-galactosidase (measured in brain and liver) were the same for shiverer and control mice. The shiverer mouse, therefore, demonstrates a dissociation between the genetic mechanisms regulating myelination in the CNS and developmental changes in enzyme activities thought to be closely related to the synthesis of myelin. In addition, we found no defect in the shiverer mouse in the incorporation of glycine-labeled basic protein into CNS myelin, indicating an important metabolic difference between the morphologically similar shiverer and quaking mutants.

The biosynthesis of sulphogalactosyldiacylglycerol of rat brain in vitro

Triton X-100 extracts of rat brain microsomal fraction catalyse the formation of sulphogalactosyldiacylglycerol from galactosyldiacylglycerol and adenosine 3'-phosphate 5'-sulphatophosphate. Of the various subcellular fractions of brain assayed, the microsomal fraction contained most (79%) of the adenosine 3'-phosphate 5'-sulphatophosphate-galactosyldiacylglycerol sulphotransferase activity. The enzyme activity was stimulated by Triton X-100 and showed linearity with increasing time, concentrations of enzyme and added substrates. ATP and KF prolonged the linearity of the activity with time, but ATP had an overall inhibitory effect on the sulphotransferase. Both ATP and KF inhibit the degradation of adenosine 3'-phosphate 5'-sulphatophosphate, which probably causes the increased linearity of the sulphotransferase reaction with time. The enzyme preparation did not catalyse the transfer of sulphate from adenosine 3'-phosphate 5'-sulphatophosphate to either cholesterol or galabiosyldiacylglycerol (galactosylgalactosyldiacylglycerol). Significant differences between the formation of sulphogalactosyldiacylglycerol and cerebroside sulphate catalysed by the same enzyme preparation were noted. ATP and Mg(2+) strongly inhibit the formation of sulphogalactosyldiacylglycerol but equally strongly stimulate the synthesis of cerebroside sulphate. The apparent K(m) for galactosyldiacylglycerol is 200mum, and that for cerebroside is 45mum. Galactosyldiacylglycerol and cerebroside are mutually inhibitory toward the synthesis of sulphated derivatives of each. These data do not necessarily lead to the conclusion that two sulphotransferases are present, but they do indicate a possible means of controlling the synthesis of these two sulpholipids.

3'-phosphoadenylylsulfate:galactosylceramide 3'-sulfotransferase. An optimized assay in homogenates of developing brain

An optimized in vitro assay of 3'-phosphoadenylysulfate:galactosylceramide 3'-sulfotransferase (EC 2.8.2.11, galactosylceramide sulfotransferase, formerly known as galactocerebroside sulfotransferase) activity is presented, that can be used in crude homogenate of brain tissue of various developmental stages. The enzyme activity is determined by measuring the [35S]sulfatides formed by the enzymic transfer of [35S]sulfate from 3'-phosphoadenoside 5'-phospho [35S]sulfate to galactosylceramides. The sulfatide formation at 30 degrees C is linear up to 30 min and up to a protein concentration of 1 mg per 0.5 ml assay volume. The presence of 0.4% Triton X-100 and 50 micrometer exogenous bovine cerebrosides are optimal for enzyme activity. The pH optimum of the reaction is at pH 6.5 using 0.1 M imidazole buffer. The enzyme reaction is stimulated by NaCl, KCl, MgCl2, CaCl2, MnCl2, ATP and inhibited by ADP. The developmental enzyme activity pattern of mouse brain is the same, if derived from homogenates and microsomes, respectively, under our assay conditions.