METHYLOTROPHIC YEAST-CELLS AS A BIOACTIVE COMPONENT FOR SENSOR DEVELOPMENT .1. BIOCHEMISTRY OF FORMALDEHYDE-INDUCED ACIDIFICATION OF THE EXTRACELLULAR MEDIUM

Washed cells of the methylotrophic yeast Hansenula polymorpha acidify the incubation medium if it contains formaldehyde. In contrast to meth anol, formaldehyde induces a constitutive kind of medium acidification which is only insignificantly influenced by the type of growth substr ate (methanol, ethanol, glycerol, or glucose). The process is accompan ied by formate accumulation in the incubation medium. It is sensitive to azide, antimycin A, and ortho-vanadate, a protonophoric uncoupler a nd plasmalemma H+-ATPase inhibitor. Studies were conducted on: 1) the medium-acidifying capacity of mutant yeast cells with genetically defe ctive methanol and formaldehyde exchange reactions; 2) its specificity to the inducer (methanol or formaldehyde); and 3) the enzyme characte ristics of cells cultivated with different carbon sources. Blocking fo rmaldehyde reductase does not result in a significant increase in acid ification rate with formaldehyde or methanol. Disruption of alcohol ox idase and formate dehydrogenase induction by formate anions drasticall y enhances the specificity of the acidification response to formaldehy de.