'antienzyme' is formed in Modern English from the prefix 'anti-' (from Greek 'anti-' meaning 'against') combined with 'enzyme' (from New Latin/Modern Greek 'enzymon').

'enzyme' derives from Greek 'enzymon' (literally 'in leaven'), passed into New Latin and then into English as 'enzyme'; the element 'anti-' comes from Greek 'anti-' meaning 'against', and the compound 'antienzyme' is a modern English formation combining these elements.

Literally it means 'against an enzyme'; in modern usage it refers specifically to either an antibody against an enzyme or a substance that inhibits enzyme activity.