Affiliation:
1. Research Institute for Advanced Studies, Baltimore, Maryland
Abstract
Aleem
, M. I. H. (Research Institute for Advanced Studies, Baltimore, Md.). Thiosulfate oxidation and electron transport in
Thiobacillus novellus
. J. Bacteriol.
90:
95–101. 1965.—A cell-free soluble enzyme system capable of oxidizing thiosulfate was obtained from
Thiobacillus novellus
adapted to grow autotrophically. The enzyme systems of autotrophically grown cells brought about the transfer of electrons from thiosulfate to molecular oxygen via cytochromes of the
c
and
a
types; the reactions were catalyzed jointly by thiosulfate oxidase and thiosulfate cytochrome
c
reductase. The levels of both of these enzymes were markedly reduced in the heterotrophically grown organism. Cell-free extracts from the autotrophically grown
T. novellus
catalyzed formate oxidation and enzymatically reduced cytochrome
c
with formate. Both formate oxidation and cytochrome
c
reduction activities were abolished under heterotrophic conditions. The thiosulfate-activating enzyme S
2
O
3
−2
-cytochrome
c
reductase, as well as thiosulfate oxidase, was localized chiefly in the soluble cell-free fractions, and the former enzyme was purified more than 200-fold by ammonium sulfate fractionation and calcium phosphate gel adsorption procedures. Optimal activity of the purified enzyme occurred at
p
H 8.0 in the presence of 1.67 × 10
−1
m
S
2
O
3
−2
and 2.5 × 10
−4
m
cytochrome
c
. The thiosulfate oxidase operated optimally at
p
H 7.5 and thiosulfate concentrations of 1.33 × 10
−3
to 3.33 × 10
−2
m
in the presence of added cytochrome
c
at a concentration of 5 × 10
−4
m
. Both enzymes were markedly sensitive to cyanide and to a lesser extent to some metal-binding agents. Although a 10
−3
m
concentration of
p
-hydroxymercuribenzoate had no effect on S
2
O
3
−2
-cytochrome
c
reductase, it caused a 50% inhibition of S
2
O
3
−2
oxidase, which was completely reversed in the presence of 10
−3
m
reduced glutathione. Carbon monoxide also inhibited S
2
O
3
−2
oxidase; the inhibition was completely reversed by light.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
56 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献