Evidence for two subclasses of methylamine dehydrogenases with distinct large subunits and conserved PQQ-bearing small subunits

Antibodies, which were raised to the isolated subunits of the methylamine dehydrogenases of <it>Paracoccus denitrificans</it> and bacterium W3A1, were used to demonstrate immunological cross-reactivity between the small pyrrolo-quinoline quinone bearing subunits of these two enzymes. The small subunits of these enzymes also exhibited nearly identical p<it>I</it> values. Conversely, the large subunits of the <it>P. denitrificans</it> and bacterium W3A1 enzymes did not cross-react immunologically and exhibited, respectively, very acidic and very basic p<it>I</it> values which reflected the electrostatic properties of their respective holoenzymes. Antibodies specific for the large subunit of the <it>P. denitrificans</it> enzyme, but not the bacterium W3A1 enzyme, cross-reacted with the analogous proteins in cell extracts of <it>Thiobacillus versutus</it> and <it>Methylobacterium</it> sp strain AM1.