|Budget Amount *help
¥2,300,000 (Direct Cost : ¥2,300,000)
Fiscal Year 1997 : ¥900,000 (Direct Cost : ¥900,000)
Fiscal Year 1996 : ¥1,400,000 (Direct Cost : ¥1,400,000)
Alcohol dehydrogenase (ADH) of acetic acid bacteria functions as the primary dehydrogenase of the ethanol oxidase respiratory chain, where it donates electrons to ubiquinone. ADH is a membrane-bound quinohemoprotein-cytochrome c complex which consists of the subunits, I,II and III,and contains four hemes c as well as pyrroloquinoline quinone as prosthetic groups. In addition to normal ADH (active ADH), Gluconobacter suboxydans produces inactive ADH which has been purified and shown to have the same subunit composition and prosthetic groups as active ADH.This research project was performed to elucidate the generation mechanism and also the physiological function of inactive ADH,and the following results have been obtained durint the course.
1) As well as Gluconobacter stains, such an inactive ADH was shown to be produced in Acetobacter species by changing the culture conditions.
2) In Gluconobacter suboxydans, conversion from inactive to active ADH was shown to occur even in the resting cells, but not in the spheroplast, in the presence of respiratory substrate.
3) Hybrid ADH could be prepared from subunit II of Acetobacter methanolicus and subunit I/III complex of Gluconobacter suboxydans. One of the hemes c moieties was shown to be largely changed in the hybrid enzyme by comparing the kinetic properties and the redox potentials of native ADH.
4) The redox potentials were compared between active and inactive ADHs of Gluconobacter suboxydans, and also in Acetobacter aceti, the kinetic property of inactive ADH was compared with active ADH,suggesting that one of 4 hemes c is also changed in the property in both Bluconobacter suboxydans and Acetobacter aceti.
5) Both active and inactive ADHs were shown to have a novel function, ubiquinol oxidase activity, besides ubiquinone reduction activity with ethanol. The ubiquinol oxidase activity was also shwon to be increased in inactive ADH.