Table 2

Immunoinhibition analysis of catalytic competence of inside and outside exposed PM CYP2D6

Type of membranes	Control antibodies	Anti-2D6 antibodies	Dextromethorphan conversion per unit of CPR^2-a
PM			11 ± 2
PM	External^2-b		12 ± 1
PM		External^2-b	0.6 ± 0.1
PM	External^2-b + internal^2-c		13 ± 2
PM		External^2-b + internal^2-c	0 ± 0
PM	External^2-b	Internal^2-c	0.0 ± 0.1
PM	Internal^2-c	External^2-b	1.0 ± 0.2
Homogenate	External^2-b		7 ± 1
Homogenate		External^2-b	7 ± 1

Spheroplasts were incubated for 1 hr on ice with anti-CYP2D6 or control antibodies (diluted 1:50 in 1.2 m sorbitol and PBS). After three washes, the incubated spheroplasts were attached on the silica microbeads for PM preparations. Before disruption of bead-bound spheroplasts, an aliquot was taken to prepare an homogenate to monitor the intracellular P450 activity. Values are the mean ± standard deviation (two replicates on three independent cultures).

↵2-a Arbitrary unit.
↵2-b Spheroplasts were first incubated with antibodies and washed before disruption.
↵2-c Isolated plasma membranes were incubated with antibodies before the activity assays.