We have recently demonstrated the mechanistic similarities
of the Class I PhaCRe and a Class III Allochromatium
vinosum PHA synthase (PhaECAv) (27, 28).
However, the kinetics of PhaECAv, while biphasic, involve
a rapid release of CoA followed by a slower release
of CoA. The substrate specificity of this enzyme
has also been examined and provides an additional
comparison of these two classes of enzymes. The differences
between our in vitro studies and those of others,
and in vivo results on both Class I and III PHA
synthases are compared.