Several enzyme activities are indicated at different sites of the same protein (large polypeptide) macromolecule for catalyzing different consecutive reactions of a metabolic pathway. So long the molecule stays as a single molecule its active sites catalyze the respective reactions in a specific sequence and release the final product. Such a macromolecule is called a multienzyme complex or system. Example- cytoplasmic fatty acid synthase complex, aspertate transcarboamylase etc. and mitochondrial pyruvate dehydrogenase, glycine cleavage enzyme etc.