Lipstatin is a potent, irreversible inhibitor of

pancreatic lipase Triglyceride lipases () are a family of lipolytic enzymes that hydrolyse ester linkages of triglycerides. Lipases are widely distributed in animals, plants and prokaryotes. At least three tissue-specific isozymes exist in higher vertebrates, p ...

. It is a

natural product A natural product is a natural compound or substance produced by a living organism—that is, found in nature. In the broadest sense, natural products include any substance produced by life. Natural products can also be prepared by chemical syn ...

that was first isolated from the

actinobacterium The ''Actinomycetota'' (or ''Actinobacteria'') are a phylum of all gram-positive bacteria. They can be terrestrial or aquatic. They are of great economic importance to humans because agriculture and forests depend on their contributions to so ...

Streptomyces toxytricini ''Streptomyces toxytricini'' is a Gram-positive bacterium belonging to the genus ''Streptomyces''. It produces the pancreatic lipase inhibitor lipstatin, of which the antiobesity drug orlistat Orlistat, sold under the brand name Xenical amon ...

''. The popular

antiobesity Anti-obesity medication or weight loss medications are pharmacological agents that reduce or control weight. These medications alter one of the fundamental processes of the human body, weight regulation, by altering either appetite, or absor ...

drug

orlistat Orlistat, sold under the brand name Xenical among others, is a medication used to treat obesity. Its primary function is preventing the absorption of fats from the human diet by acting as a lipase inhibitor, thereby reducing caloric intake. It ...

(trade names Xenical and alli) is a

saturated Saturation, saturated, unsaturation or unsaturated may refer to: Chemistry * Saturation, a property of organic compounds referring to carbon-carbon bonds ** Saturated and unsaturated compounds **Degree of unsaturation ** Saturated fat or fatty ac ...

derivative of lipstatin.

Biosynthesis

Lipstatin is composed of a 2-hexyl-3,5-dihydroxy-7,10-hexadecadienoic-β-lactone 22 carbon backbone from

fatty acid synthesis In biochemistry, fatty acid synthesis is the creation of fatty acids from acetyl-CoA and NADPH through the action of enzymes called fatty acid synthases. This process takes place in the cytoplasm of the cell. Most of the acetyl-CoA which is conve ...

pathway and an ''N''-formyl-

L-leucine Leucine (symbol Leu or L) is an essential amino acid that is used in the biosynthesis of proteins. Leucine is an α-amino acid, meaning it contains an α-amino group (which is in the protonated −NH3+ form under biological conditions), an α- ca ...

group ester linked to the 5-hydroxyl group of the back bone. The composts of the lipstatin are ultimately from

linoleic acid Linoleic acid (LA) is an organic compound with the formula COOH(CH2)7CH=CHCH2CH=CH(CH2)4CH3. Both alkene groups are cis-trans isomerism, ''cis''. It is a fatty acid sometimes denoted 18:2 (n-6) or 18:2 ''cis''-9,12. A linoleate is a salt (chem ...

octanoic acid Caprylic acid (), also known under the systematic name octanoic acid or C8 Acid, is a saturated fatty acid, medium-chain fatty acid (MCFA). It has the structural formula , and is a colorless oily liquid that is minimally soluble in water with a s ...

, and

. The 22 carbon β-lactone moiety is derived from

Claisen condensation The Claisen condensation is a carbon–carbon bond forming reaction that occurs between two esters or one ester and another carbonyl compound in the presence of a strong base, resulting in a β-keto ester or a β-diketone. It is named after Raine ...

between 3-hydroxytetradeca-5,8-dienyl-CoA derived from

and hexyl-malonyl-ACP derived from

. Linoleic acid is first attached to CoA through some acyl-CoA synthetase homologue synthesized by lipstatin biosynthetic operons (''Lst'') and goes through two

β-oxidation In biochemistry and metabolism, beta-oxidation is the catabolic process by which fatty acid molecules are broken down in the cytosol in prokaryotes and in the mitochondria in eukaryotes to generate acetyl-CoA, which enters the citric acid cycle, ...

to hydroxytetradeca-5,8-dienyl-CoA. 3’ hydroxyl group from solution H₂O is added by enoyl reductase homologue followed by enoyl hydratase homologue. Octanoic acid is also attached to CoA through similar acyl-CoA synthetase homologue (''LstC'') to form

octanoyl-CoA Octanoyl-coenzyme A is the endpoint of beta oxidation in peroxisomes. It is produced alongside acetyl-CoA and transferred to the mitochondria to be further oxidized into acetyl-CoA. See also *Caprylic acid Caprylic acid (), also known under ...

. Octanoyl-CoA is 2’ carboxylated and loaded to

acyl carrier protein The acyl carrier protein (ACP) is a cofactor of both fatty acid and polyketide Polyketides are a class of natural products derived from a precursor molecule consisting of a chain of alternating ketone (or reduced forms of a ketone) and methylene ...

(ACP) borrowed from primary metabolism to form hexyl-malonyl-ACP. The β-lactone ring is formed by reduction of 3-

keto group In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bon ...

by 3-hydroxysteroid

dehydrogenase A dehydrogenase is an enzyme belonging to the group of oxidoreductases that oxidizes a substrate by reducing an electron acceptor, usually NAD+/NADP+ or a flavin coenzyme such as FAD or FMN. Like all catalysts, they catalyze reverse as well as f ...

homologue followed by a spontaneously

nucleophilic attack In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are ...

of the 3-

hydroxyl group In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydroxy g ...

on the carbonyl of the ACP-tether acyl intermediate. This step follows the

esterification In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...

of the ''N''-formyl-L-leucine group. The ''N''-formyl-L-leucine group is derived from

. L-leucine was activated by ''LstE'' forming

thioester In organic chemistry, thioesters are organosulfur compounds with the functional group . They are analogous to carboxylate esters () with the sulfur in the thioester playing the role of the linking oxygen in the carboxylate ester, as implied by t ...

and its α-amine group is formylated by ''LstF''. Finally, 5-hydroxyl of 22 carbon β-lactone backbone nucleophilic attacks on the acyl carbon of the formyl-leucine and forms the lipstatin.

References

{{Reflist Hydrolase inhibitors Lactones Oxetanes Carboxylate esters Formamides Lipase inhibitors