P. Wang et al., EXPRESSION, PURIFICATION, AND CHARACTERIZATION OF HUMAN CAMP-SPECIFICPHOSPHODIESTERASE (PDE4) SUBTYPE-A,SUBTYPE-B, SUBTYPE-C, AND SUBTYPE-D, Biochemical and biophysical research communications, 234(2), 1997, pp. 320-324
Although four members (A, B, C, and D) of the cAMP-specific phosphodie
sterase (PDE4) family have been cloned by different groups, no study c
omparing the characteristics of purified human PDE4 subtypes has been
published. In this study, we have expressed human PDE4 A, B, C, and D
in insect (SF9) cells by using the baculovirus expression system, puri
fied the expressed proteins, and compared their characteristics. The r
ecombinant PDE4 subtypes all showed catalytic activity for cAMP with a
K-m of 1-5 mu M. V-max values differed significantly among these subt
ypes with the following order: C > B > A > D. PDE4 A, B, C, and D show
ed a very similar Mg2+ dependence profile. PDE4 B and C showed similar
pH profiles with the optimal pH being 8.0. The pH profiles of PDE4 A
and D were very different from each other and from those of B and C, w
ith the optimal pH being 6.5 and 7.5, respectively. Furthermore, altho
ugh PDE4 A, B, C, and D were all inhibited by the standard PDE4 inhibi
tors rolipram, Ro20-1724, and etazolate, the inhibitory potency varied
. Thus, by several criteria including kinetics, pH dependency, and inh
ibitor sensitivity, various PDE4 subtypes differ significantly from on
e another. (C) 1997 Academic Press.