. Cell chemistry; a collection of papers dedicated to Otto Warburg on the occasion of his 70th birthday. Warburg, Otto Heinrich, 1883-; Biochemistry. 310 F. LYNEN, S. OCHOA VOL. 12 (1953) of r^-/9-hydroxybutyryl-S-CoA by DPN+. The latter reaction, which is undoubtedly catalyzed by the ^-ketoreductase here described, was demonstrated by making use of the fact that liver also contains enzymes catalyzing the formation of d- or /-jS-hydroxy- butyryl-S-CoA in the presence of ATP, CoA-SH, and d- or /-j8-hydroxybutyrate. The chain-length specificity of the ^-ketoreductase is still unknown and it is n
. Cell chemistry; a collection of papers dedicated to Otto Warburg on the occasion of his 70th birthday. Warburg, Otto Heinrich, 1883-; Biochemistry. 310 F. LYNEN, S. OCHOA VOL. 12 (1953) of r^-/9-hydroxybutyryl-S-CoA by DPN+. The latter reaction, which is undoubtedly catalyzed by the ^-ketoreductase here described, was demonstrated by making use of the fact that liver also contains enzymes catalyzing the formation of d- or /-jS-hydroxy- butyryl-S-CoA in the presence of ATP, CoA-SH, and d- or /-j8-hydroxybutyrate. The chain-length specificity of the ^-ketoreductase is still unknown and it is not possible to decide at this time whether more than one enzyme is concerned with the CoA derivatives of j3-keto and /^-hj^droxy acids from C4 to C^g. The purified reductase described above has been found to act rapidly on S-/S-ketocaproyl-N-acetyl thioethanolamine^^^. Crotonaso. Synthetic S-crotonyl CoA is converted to S-acetoacetyl CoA, in the pres- ence of DPN, by crude enzyme preparations from heart or liver^'''. The reaction can be followed through the appearance of the absorption band of DPNH at 340 mju, or that of acetoacetyl-S-CoA at 305 m/x. Also, on addition of HS-CoA, citrate condensing enzyme, and oxalacetate, crotonyl-S-CoA acts as an acetyl donor for citrate synthesis; the required thiolase was present in the crude enzyme preparation used. These observations, together with the fact that reduced leucosafranine is oxidized by synthetic j3-hydroxy- butyryl-S-CoA in the presence of partially purified preparations of ethylene reductase^^ indicate the occurrence of an enzyme catalyzing the reversible Reaction 7 below. The name crotonase has been for this enzyme^^. The enzyme has no action on free o o CH.,—CH = CH—C—S—CoA + HoO ^ CH.,—CHOH—CH„—C—S—CoA (7) crotonate or on the S-crotonyl derivatives of N-acetyl thioethanolamine, glutathione or thioglycolic acid. As already mentioned the spectrum of S-crotonyl CoA is similar to tha
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