Question

How can 1-stearoyl, 2-oleoyl, 3-palmitoyl glycerol be biosynthesized from acetyl-coa? Please include the biosynthesis of all central components of the lipid and any additional components that may be required for its synthesis (exclude cofactors and proteins).

Answer 1

1 stearoyl,2 oleoyl,3 palmitoyl is a monostearic acid triglyceride [TG]. They are the main constituents of vegetable oils and animal fats. Each molecule contains a chain of palmitic acid at C-1 position, one chain of stearic acid at C-2 position and one chain of oleic acid at C-3 position.

The major building block for synhesis of triglycerides in non- adipose tissue are glycerols. Adipose cells lack glycerol kinase and hence, use another route for TAG synthesis . So, in the adipose tissues TAG synthesis is done from dihydroxy acetone phosphate [DHAP], which is produced during glycolysis. DHAP can also be a precursor of TAG in non-adipose tissue , but to a lesser extent than glycerol.

The use of DHAP for the TAG backbone de[pends on whether its synthesis occurs in the mitochondria and ER or the ER and the peroxisomes.In the mitochondria/ ER pathway the following sequence of events occur--

* glycerol 3 phosphate dehydrogenase converts DHAP to glycerol 3 phosphate.

* glycerol 3 phosphate acyltransferase then esterifies a fatty acid to glycerol 3 phosphate thereby generating lysophosphatidic acid .

In the ER/peroxisome reaction pathway uses DHAP acyltransferase to acylate DHAP to acyl-DHAP , which is then reduced by acyl-DHAP reductase.

The fatty acids that are incorporated into TAG are activated to acyl-CoA through the action of acyl-CoA SYNTHETASE.

Two molecules of acyl-CoA are esterified to glycerol-3-phosphate to yield 1,2-diacylglycerol phosphate , also known as phosphatidic acid.

The phosphate is then removed by phosphatidic acid phosphatase to generae 1,2-diacylglycerol.

This diacylglycerold serves as the substrate for addition of the third fatty acid to make TAG.