-!- Essential, along with EC 2.3.1.39, for the initiation of fatty-acid biosynthesis in bacteria. -!- The substrate acetyl-CoA protects the enzyme against inhibition by N-ethylmaleimide or iodoacetamide. -!- This is one of the activities associated with EC 2.3.1.180.

-!- This enzyme is responsible for the dehydration step of the dissociated (type II) fatty-acid biosynthesis system that occurs in plants and bacteria. -!- The enzyme uses fatty acyl thioesters of ACP in vivo. -!- Different forms of the enzyme may have preferences for substrates with different chain length. -!- For example, the activity of FabZ, the ubiquitous enzyme in bacteria, decreases with increasing chain length. -!- Gram-negative bacteria that produce unsaturated fatty acids, such as Escherichia coli, have another form (FabA) that prefers intermediate chain length, and also catalyzes EC 5.3.3.14. -!- Despite the differences both forms can catalyze all steps leading to the synthesis of palmitate (C16:0). -!- FabZ, but not FabA, can also accept unsaturated substrates. -!- Formerly EC 4.2.1.58, EC 4.2.1.60 and EC 4.2.1.61.

-!- The enzyme from yeasts (Ascomycota and Basidiomycota) is a multi- functional protein complex composed of two subunits. -!- One subunit catalyzes the reactions EC 1.1.1.100 and EC 2.3.1.41, while the other subunit catalyzes the reactions of EC 2.3.1.38, EC 2.3.1.39, EC 4.2.1.59, EC 1.3.1.10 and EC 1.1.1.279. -!- The enzyme differs from the animal enzyme (EC 2.3.1.85) in that the enoyl reductase domain requires FMN as a cofactor, and the ultimate product is an acyl-CoA (usually palmitoyl-CoA) instead of a free fatty acid.

-!- Essential, along with EC 2.3.1.38, for the initiation of fatty-acid biosynthesis in bacteria. -!- Also provides the malonyl groups for polyketide biosynthesis. -!- The product of the reaction, malonyl-ACP, is an elongation substrate in fatty-acid biosynthesis. -!- In Mycobacterium tuberculosis, holo-ACP (the product of EC 2.7.8.7) is the preferred substrate. -!- This enzyme also forms part of the multienzyme complexes EC 4.1.1.88 and EC 4.1.1.89. -!- Malonylation of ACP is immediately followed by decarboxylation within the malonate-decarboxylase complex to yield acetyl-ACP, the catalytically active species of the decarboxylase. -!- In the enzyme from Klebsiella pneumoniae, methylmalonyl-CoA can also act as a substrate but acetyl-CoA cannot whereas the enzyme from Pseudomonas putida can use both as substrates. -!- The ACP subunit found in fatty-acid biosynthesis contains a pantetheine-4'-phosphate prosthetic group; that from malonate decarboxylase also contains pantetheine-4'-phosphate but in the form of a 2'-(5-triphosphoribosyl)-3'-dephospho-CoA prosthetic group.

-!- The enzyme catalyzes an essential step in fatty acid biosynthesis, the reduction of the 2,3-double bond in enoyl-acyl-[acyl-carrier- protein] derivatives of the elongating fatty acid moiety. -!- The enzyme from the bacterium Escherichia coli accepts substrates with carbon chain length from 4 to 18. -!- The FAS-I enzyme from the bacterium Mycobacterium tuberculosis prefers substrates with carbon chain length from 12 to 24 carbons.

-!- Acts on [acyl-carrier-protein] thioesters of fatty acids from C(12) to C(18), but the derivative of oleic acid is hydrolyzed much more rapidly than any other compound tested.