The oxidation of dithiols

A respiratory catalyst required for the reduction of cytochrome c by cytochrome b

“…It is known that BAL has a destructive effect on some haematin compounds. Thus, Barron, Miller & Kalnitsky (1947) have shown that haemoglobin is destroyed by treatment with BAL in the presence of air, and, in the present investigation, it was found that myoglobin was similarly 24 I949 affected. This reaction is probably essentially the same as that between haemoglobin and another reducing agent, ascorbic acid, which has been studied in detail by Lemberg, Legge & Lockwood (1941).…”

“…The larger inhibition of the succinic dehydrogenase found with ascorbic acid compared with BAL may be due to the failure of ascorbic acid (Eo = 0-05 V., at pH 7-3, 300; Ball, 1937) to protect the SH groups of succinic dehydrogenase from oxidation by H202. BAL with an E' of -0-15 V. at pH 7-0 (Barron, Miller & Kalnitsky, 1947) is more favourably situated in this respect. The greater inhibition with cysteine is probably related to the more rapid oxidation of this compound which might be expected to behave in the same way as BAL, if a shorter time of reaction were used.…”

“…The evidence for this is: (1) the inactivation, which occurs only when the reducing agent is added to the enzyme preparation in the presence of air, bears a striking resemblance to the effect of reducing agents on haemoglobin (Lemberg et al 1941); (2) BAL has been shown to destroy haematin itself and haemoglobin (Barron, Miller & Kalnitsky, 1947), myoglobin (this investigation) and the haematinenzymes peroxidaseand catalase (Webb & van Heyningen, 1947;Lemberg & Foulkes, 1948), while glutathione inhibits catalase (Marks, 1936); (3) quantitative measurements of the amount of haematin compounds in the heart-muscle and kidney preparations suggest that these preparations contain haematin compounds, whose spectra are not visible (Slater, 1949a); (4) some protohaematin compound is destroyed by treatment of the heart-muscle preparation with BAL, and the destruction of this, compound is parallel to the inactivation of the succinic oxidase system. It is interestingtonote that thenaturally occurring haematin compounds fall into two groups, according to the nature of their absorption spectra and their susceptibility to reducing agents, viz.-Group A: peroxidase, catalase and methaemoglobin; these compounds, whether in the ferric or the ferrous state, possess rather weak absorption bands.…”

“…Table 6 shows that the rate of oxidation of BAL was increased 2-5 times by the presence of the heart-muscle preparation, and doubled by the presence of the kidney preparation. Since Barron, Miller & Kalnitsky (1947) have reported that copper catalyses the oxidation of BAL, the possibility that this increased rate of oxidation might be largely due to copper in the heart-muscle preparation was investigated. It was found by direct analysis that the heart-muscle preparation contained sufficient copper (4.2 x 10-5 M) to account for its catalytic effect on the oxidation of BAL, provided that this copper was as effective as Cu++ ions added to the preparation.…”

Mechanism of Inactivation of Bacteriophage J 1 by Dithiothreitol, Cysteine, Mercaptoethanol, or Thioglycollate

“…1) Thiol themselves are known to act potentially as radical scavengers, i.e., they are able to scavenge the free radicals which are responsible for the breakage in DNA. Since solutions of DTT and the like are known to be much more stable to air oxidation than glutathione, 5,6) i.e., in the production rate of radical DTT and the like are much slower than glutathione, the rate of scavenging radicals may be more rapid than the production rate of radicals at high concentrations of DTT and the like. 2) After the phage inactivation by DTT had occurred, active phage could be recovered by the addition of high concentrations of DTT to the inactivated phage solution (Fig.…”