Enzyme has recently rebranded from Melon Protocol. The protocol has been on main-net since Feb 2019 and was the first DeFi protocol in history to decentralise it's governance. Enzyme v2 was launched to main-net in Jan 2021 and is a completely re-architected protocol with modularity and extensibility at the core of it's design.
Enzyme’s token is MLN and has a dual use. It is 1) used to pay fees to the network by users and 2) used to incentivise developers to build on Enzyme. There is currently a well-supported proposal to change the token's economic model. Details can be found here.
Enzyme is governed by a DAO known as the Enzyme Council which is made up of technical experts and user representatives. A complete discussion of the protocol's governance can be found here.