FMO5 and chronic granulomatous disease: This defective acidification of neutrophil phagosomes is largely attributed to the reduced insertion of proton-pumping vacuolar-type (V-type) ATPases into the phagosomal membrane in the presence of an active NADPH oxidase [84] and the consumption of protons during dismutation of NADPH oxidase-derived superoxide, since the lack of NADPH oxidase seen in CGD patients or chemical inhibition of this enzyme led to a rapid and extensive fall in pH [85].