Taste bud adenosine -3'5'-monophosphate phosphodiesterase: activity, subcellular distribution and kinetic parameters

Higher activity of cyclic adenosine 3',5'-monophosphate (cAMP) phosphodiesterase (PDE) was found in homogenates from bovine circumvellate papillae bearing taste buds compared to activity in homogenates from areas surrounding these papillae in which no taste buds were present. With progressive purification of these homogenates cAMP PDE activity increased in the taste bud enriched fractions relative to that measured in the non-taste bud bearing epithelial tissue. The highest levels of cAMP PDE activity were measured in those taste bud fractions in which purification was greatest. Kinetic studies in both taste bud derived and control tissues showed two apparent Km values, one relatively high, the other, lower. cAMP PDE activity of taste bud membranes was enhanced by Mg++, Mn++ and imidazole and inhibited by ethylene-bis (beta-aminoethylether) N,N-tetra-acetic acid (EGTA), isobutyl methyl xanthine (IBMX), theophylline, and cyclic guanosine 3',5'-monophosphate (cGMP). The possible role for cAMP PDE in taste function is discussed.