. The chemistry and mode of action of plant growth substances; proceedings of a symposium held at Wye College, University of London, July 1955. Plant regulators; Auxin; Growth (Plants). The influence of growth substances upon sulphydryl compounds In this system acetate is transferred from acetyl phosphate to CoA enzymati- cally, and the rate of this acetylation is proportional to the amount of functional CoA present. A linear relationship between the disappearance of acetyl phosphate and the quantity of CoA present is obtained from 0 to 5xlO~^MCoA. Under the conditions utilized the acetyl phos
. The chemistry and mode of action of plant growth substances; proceedings of a symposium held at Wye College, University of London, July 1955. Plant regulators; Auxin; Growth (Plants). The influence of growth substances upon sulphydryl compounds In this system acetate is transferred from acetyl phosphate to CoA enzymati- cally, and the rate of this acetylation is proportional to the amount of functional CoA present. A linear relationship between the disappearance of acetyl phosphate and the quantity of CoA present is obtained from 0 to 5xlO~^MCoA. Under the conditions utilized the acetyl phosphate remaining after 15 minutes was measured by the ferric hydroxamic acid test. ~ i^2x10''^W. I 0 5xio~^y\ 5x10'^ 5x10''' Concn. of growth substance • Figure 10. Reaction of CoA with TIB A and 2-A-D. Final concentrations of constituents: 2-5 X 10-* M Co J 5X10-2M TRISpH 8 growth substances as indicated. Volume: 0-2 ml. Incubation time: 60 minutes. Temperature: 30". Functional CoA remaining after incubation estimated according to Stadtman (1952), except that the cysteine was deleted. The effects of TIBA and 2:4-D upon the reaction of CoA are shown in Figure 10. It can be seen that while 2:4-D was only slightly inhibitory, TIBA at 5 X 10^^ M completely destroyed the effectiveness of CoA in this reaction. There is approximately one hundred times as much of the growth substance as CoA present, but the time of incubation of the growth substance with CoA was only one hour. An increasing effectiveness of the growth substance TIBA with increasing time of incubation can be seen in Figure 11. It is strongly suggested from these data that TIBA may interfere with the acyl transfer functions of CoA through reaction with the sulphydryl group of the coenzyme. Earlier work on sulphydryl inactivating agents has frequently shown a reversal of the inactivation with cysteine. Dickens (1933) reports such a reversal of iodoacetic acid inhibition of rat liver glyoxalase and suggests from his
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