A cyclase is an enzyme, almost always a lyase, that catalyzes a chemical reaction to form a cyclic compound. Important cyclase enzymes include:

Adenylyl cyclase, which forms cyclic AMP from adenosine triphosphate (EC 4.6.1.1)

• ADCY1

• ADCY2

• ADCY3

• ADCY4

• ADCY5

• ADCY6

• ADCY7

• ADCY8

• ADCY9

• ADCY10

Guanylyl cyclase, which forms cyclic GMP from guanosine triphosphate (EC 4.6.1.2)

• GUCY1A2

• GUCY1A3

• GUCY1B3

• Guanylate cyclase 2C

• Guanylate cyclase 2D

• Guanylate cyclase 2F

• NPR1

• NPR2

• Protein cyclase, a ligase enzyme that produces backbone-cyclised proteins by intramolecular transpeptidation