Lactose operon (model proposed by Jacob and Monad) produces three enzymes -$ b-$ galactosidase $(z)$, permease $(y)$, transacetylase $(a) . $b-\; Galactosidase $(z)$ is responsible for the splitting of lactose into glucose and galactose. Permease $(y)$ is required in entry of the lactose/galactose. Transacetylase $(a)$ transfers an acetyl $CoA$ to $ b-$Galactosides.