Histamine (3) which taken as the reference compound have the [K.sub.A] values against hCAI and hCAII of 2 [micro]M, and 125 [micro]M, respectively, being a highly potent activator against both the isoforms (Table 1).
(22-25) The hCAI and hCAII isozymes were eluted with 1 M NaCl/25 mM [Na.sub.2]HP[O.sub.4] (pH 6.3) and 0.1 M C[H.sub.3]COONa/0.5 M Na[ClO.sub.4] (pH 5.6), respectively.
It has the [K.sub.A] values against hCAI and hCAII of 2 [micro]M, and 125 [micro]M, respectively.
1 are typical examples of the potentiometric experiments carried out in the absence of enzymes and in the presence of hCAI, hCAII, and bCAII.
Although it is virtually impossible to obtain reliable KI values to calculate exactly the inhibitory power of each antibody in relation to the different isoenzymes, our preliminary results indicate that the interaction between CA and anti-CA antibodies is associated with a decrease in enzyme catalytic activity only in the case of specific interactions, i.e., between hCAI and aCAIabs and between hCAII (and, to a lesser extent, bCAII) and aCAIIabs.