How many biosynthetic families are know for amino acid biosynthesis.

There are six of them, based on the common compound that they are synthesized

Explanation:

The family of L - glutamate come from the cetoglutarate compound from the Kreps cycle. The family of L-serine, come from 3 - phosphoglicerate compound from the glucolisis. The L - aspartate family, that come from oxaloacetate compound, from the Krebs cylce. The piruvate family that come from the piruvate, from the glucolisis. The aromatic aminoacids, that come from eritrose - 4 - phosphate, from the pentose cycle. And the L histidine family, that come from the ATP.