What is "steroid-lactonase"

In enzymology, a steroid-lactonase is an enzyme that catalyzes the chemical reaction

testololactone + HO $\rightleftharpoons$ testolate

Thus, the two substrates of this enzyme are testololactone and HO, whereas its product is testolate.

This enzyme belongs to the family of hydrolases, specifically those acting on carboxylic ester bonds. The systematic name of this enzyme class is testololactone lactonohydrolase.