Table 1.

Number of families and subfamilies in each GPCR class

GPCRs’ Class	No. of GPCR Families	No. of GPCR Subfamilies
Class A	55	640 (422 subfamilies of olfactory receptor)
Class B	6	16
Class C	4	41 (29 subfamilies of taste receptors)
Frizzled/Smoothened	2	11
Total	67	708

Class A is the largest and consists of 55 families and 640 subfamilies (422 subfamilies of olfactory receptors). Class B consists of 6 families and 16 subfamilies. Class C consists of 4 families and 41 subfamilies (29 subfamilies of taste receptors). Frizzled/Smoothened class consists of 2 families and 11 subfamilies.