. Cell chemistry; a collection of papers dedicated to Otto Warburg on the occasion of his 70th birthday. Warburg, Otto Heinrich, 1883-; Biochemistry. Fig. 3. pH Dependence of light ab- sorption of S-acetoacetyl-N-acetyl thioethanolamine at 313 m^w. c = 5- io~^ M; d = cm. crystalline form (, °) through reaction of crotonyl chloride with the lead salt of N-acetyl thioethanolamine^^. Its absorption spectrum is shown, along with that of free crotonate, in Fig. 4. It is evident that with the binding of the unsaturated acid to sulfur there is a shift toward longer wavelengths of the a
. Cell chemistry; a collection of papers dedicated to Otto Warburg on the occasion of his 70th birthday. Warburg, Otto Heinrich, 1883-; Biochemistry. Fig. 3. pH Dependence of light ab- sorption of S-acetoacetyl-N-acetyl thioethanolamine at 313 m^w. c = 5- io~^ M; d = cm. crystalline form (, °) through reaction of crotonyl chloride with the lead salt of N-acetyl thioethanolamine^^. Its absorption spectrum is shown, along with that of free crotonate, in Fig. 4. It is evident that with the binding of the unsaturated acid to sulfur there is a shift toward longer wavelengths of the absorption due to the double bond. Free crotonate has a maximum (not shown on the figure) at 204 m fx while the thioester has a maximum at 224 m/x. The thioester has an additional band at 263 m/it which is possible due O to the —C—S-group. The shift of the two absorption maxima toward longer wavelengths may be a reflection of the resonance between the double bond and the thio- ester linkage, a fact which is of great importance for the chemical reactivity of the former. A number of S-acyl CoA derivatives of fatty acids have now become available through chemical or enzy mic synthesis. Solutions of acetoacetyl CoA can be readily prepared by the enzymic transfer of CoA from succinyl CoA to acetoacetate. This reaction has made possible the isolation of acetoacetyl CoA**^ and its rou- tine preparation for the assay of ^-ketothiolase. Succinyl CoA itself can be prepared enzymically with a-ketoglutaric dehydrogenase^*'2'^ or by means of the reaction between suc- cinate, CoA, and ATP, of Kaufman etal.^^'". However, the compound can be obtained much more readily by the syn- thetic procedure of Simon and Shemin^^ with CoA-SH and succinic anhydride. The method of Simon and Shemin has further been applied to the preparation of other S-acyl CoA derivatives such as acetyl, propionyl, butyryl, and crotonyl CoA. S-acyl fatty acid derivatives have also been prepared by means of the enzy
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