Metabolism of the plant sulfolipid--sulfoquinovosyldiacylglycerol: degradation in animal tissues.
Metabolism of the plant sulfolipid--sulfoquinovosyldiacylglycerol (SQDG)--was studied in animal tissues. In vivo experiments with [35S]SQDG in guinea pigs showed that this lipid is not absorbed intact in the gastrointestinal tract. In these experiments, 3 h after administration of [35S]SQDG, the intestinal mucosa contained 1 to 5% of the radioactivity as SQDG, while the remainder was in a water-soluble form. Analysis of the water-soluble components showed that about 60% of the radioactivity was present as sulfoquinovosylglycerol (SQG) and the remainder was present as free SO4(2-). In the blood, 99% of the radioactivity was present as SO4(2-), SQG was not observed. In liver, only very little radioactivity was observed and appeared to be mainly in the form of SO4(2-). Experiments with everted intestinal sacs of guinea pigs confirmed the formation of SQG, SO4(2-), and, in addition, sulfoquinovosylmonoacylglycerol (SQMG) in this tissue. In vitro experiments with saline extracts of acetone powders of pancreas and intestinal mucosa of guinea pig, sheep, and rat showed that [35S]SQDG was deacylated to SQMG (sulfolipase A activity) and SQG (sulfolipase B activity). It is concluded that animal tissues deacylate SQDG in a stepwise manner to SQG. It is further metabolized to yield free SO4(2-) by cleavage of the C-S bond which appears to be brought about by the intestinal microflora. Sheep pancreatic sulfolipases were characterized. Bile salts, sodium dodecyl sulfate, and Triton X-100 inhibited the pancreatic sulfolipases, while CaCl2 activated them. Substrate competition experiments and investigations on substrate specificity with a partially purified preparation indicated that relatively specific sulfolipase(s) may exist in pancreas. Among the species tested, guinea pig tissues showed the highest sulfolipase A and B activities followed sheep and rat tissues. Pancreatic enzymes were 18 to 60 times more active than intestinal enzymes.
Department of Biochemistry, Indian Institute of Science, Bangalore.
S D
SD
Gupta
P S
PS
Sastry
D000818:Animals; D006017:Glycolipids / Q000378:metabolism*; D006168:Guinea Pigs; D006863:Hydrogen-Ion Concentration; D007422:Intestines / Q000201:enzymology; D050356:Lipid Metabolism; D008055:Lipids; D010179:Pancreas / Q000201:enzymology; D051381:Rats; D012756:Sheep; D013429:Sulfatases / Q000378:metabolism*
D006017:Glycolipids; D008055:Lipids; C015518:sulfolipids; C013694:sulfoquinovosyl diglyceride; D013429:Sulfatases