ID   2.3.1.304
DE   poly[(R)-3-hydroxyalkanoate] polymerase.
AN   PHA synthase.
CA   [(R)-3-hydroxyalkanoate](n) + a (3R)-3-hydroxyacyl-CoA = [(R)-3-
CA   hydroxyalkanoate](n+1) + CoA.
CC   -!- This is the key enzyme in the biosynthesis of polyhydroxyalkanoates
CC       (PHA), linear polyesters produced by bacteria as a means of carbon
CC       and energy storage.
CC   -!- The enzyme catalyzes the stereoselective, covalent linkage of (3R)-3-
CC       hydroxyacyl-CoA thioesters in a transesterification reaction with
CC       concomitant release of coenzyme A.
CC   -!- The growing polymer is attached to a conserved active site L-cysteine
CC       residue.
CC   -!- Three types of PHA synthases have been proposed based on their
CC       substrate specificity and enzyme structure.
CC   -!- Type I and type III synthases preferentially polymerize short chain
CC       hydroxyalkanoate monomers containing 3-5 carbon atoms.
CC   -!- The difference between these two types is that type I synthases are
CC       composed of only a single subunit (PhaC), whereas type III synthases
CC       are composed of two different subunits, PhaC and PhaE. Type II
CC       synthases are also composed of a single subunit (PhaC),
CC       but preferentially polymerize monomers containing more than 5 carbon
CC       atoms.
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