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Phytoene in commercial tomatoes
252
LETTERS
TO
THE
EDITORS
Pltytoene in Commercial Tomatoes I wish to correct a misinterpretation by Rabourn and Quackenbush (1) of a sentence in a paper (2) of which I was a coauthor. It is stated (1) that we (2) did not find phytoene in commercial tomato varieties. We did, indeed, find and report (2) the presence of phytoene (and r-carotene) in the commercial variety Golden Jubilee and the commercial variety(ies) which constituted the tomato paste we analyzed. We had also reported in our first paper (3) the presence of phytoene in a large number of experimental tomato selections. The statement we made, “r-carotene and phytoene have never been reported in commercial tomato varieties,” which apparently caused the misinterpretation, referred to the period previous to our paper (2). The reason for this statement was not that analyses had shown the absence of phytoene in commercial varieties, but that analyses of commercial varieties for phytoene had not been made previously by ourselves or others. There is no basis at the present time for a comparison between our method of analysis for phytoene (2) and the method of Rabourn and Quackenbush. REFERENCES I. RABOURN, W. J., AND QUACKENBUBH, F. W., Arch. Biochem. and Biophys. 44,
159 (1953). 2. PORTER, J. W., AND LINCOLN, R. E., Arch. Biochem. 27,390 (1950). 3. PORTER, J. W., AND ZSCHEILE, F. P., Arch. Biochem. 10,547 (1946).
Biology Section, Radiological Sciences Department, General Electric Company, Richland, Washington Received July 7, 1963 The Enzymatic Transacetylation
JOHN W. PORTER
between Aromatic Amines
Studies on the acetyl acceptor enzyme for aromatic amines [arylamine acetokinase (l)] have shown that the fraction of pigeon liver containing it catalyzes a low-energy acetyl transfer between various aromatic amines, in addition to transfer from energy-rich acetyl coenzyme A (CoA). A fractionation with acetone similar to that described by Chou (1) was used. By repeated acetone precipitation a 3%fold concentration of the enzyme was obtained. The acetyl exc,hange was discovered by the use of 4-acetaminoazobenzene-4’ sulfonic acid. The free aminoazo compound is red and changes to yellow on acetylation. This permits the direct observation of an acetyl shift if a colorless arylamine is used as acceptor. The acetyl exchange between arylamines is not CoAdependent. In Table I, the acetyl transfer from the acetyl aminoazo dye to other aromatic amines is shown, and it may be seen that the rate varies considerably with the nature of the amine. It may be noted that in addition to the aromatic amines, hydroxylamine and hydrazine may act as acetyl ,acceptors. Otherwise, however, the enzyme was found to be strictly specific for arylamines.
LETTERS
TO
THE
EDITORS
Pltytoene in Commercial Tomatoes I wish to correct a misinterpretation by Rabourn and Quackenbush (1) of a sentence in a paper (2) of which I was a coauthor. It is stated (1) that we (2) did not find phytoene in commercial tomato varieties. We did, indeed, find and report (2) the presence of phytoene (and r-carotene) in the commercial variety Golden Jubilee and the commercial variety(ies) which constituted the tomato paste we analyzed. We had also reported in our first paper (3) the presence of phytoene in a large number of experimental tomato selections. The statement we made, “r-carotene and phytoene have never been reported in commercial tomato varieties,” which apparently caused the misinterpretation, referred to the period previous to our paper (2). The reason for this statement was not that analyses had shown the absence of phytoene in commercial varieties, but that analyses of commercial varieties for phytoene had not been made previously by ourselves or others. There is no basis at the present time for a comparison between our method of analysis for phytoene (2) and the method of Rabourn and Quackenbush. REFERENCES I. RABOURN, W. J., AND QUACKENBUBH, F. W., Arch. Biochem. and Biophys. 44,
159 (1953). 2. PORTER, J. W., AND LINCOLN, R. E., Arch. Biochem. 27,390 (1950). 3. PORTER, J. W., AND ZSCHEILE, F. P., Arch. Biochem. 10,547 (1946).
Biology Section, Radiological Sciences Department, General Electric Company, Richland, Washington Received July 7, 1963 The Enzymatic Transacetylation
JOHN W. PORTER
between Aromatic Amines
Studies on the acetyl acceptor enzyme for aromatic amines [arylamine acetokinase (l)] have shown that the fraction of pigeon liver containing it catalyzes a low-energy acetyl transfer between various aromatic amines, in addition to transfer from energy-rich acetyl coenzyme A (CoA). A fractionation with acetone similar to that described by Chou (1) was used. By repeated acetone precipitation a 3%fold concentration of the enzyme was obtained. The acetyl exc,hange was discovered by the use of 4-acetaminoazobenzene-4’ sulfonic acid. The free aminoazo compound is red and changes to yellow on acetylation. This permits the direct observation of an acetyl shift if a colorless arylamine is used as acceptor. The acetyl exchange between arylamines is not CoAdependent. In Table I, the acetyl transfer from the acetyl aminoazo dye to other aromatic amines is shown, and it may be seen that the rate varies considerably with the nature of the amine. It may be noted that in addition to the aromatic amines, hydroxylamine and hydrazine may act as acetyl ,acceptors. Otherwise, however, the enzyme was found to be strictly specific for arylamines.