N-Carbobenzoxy-4-ketoproline

In an attempt to learn whether collagen hydroxyproline synthesized in granuloma minces incubated with tritiated proline contained tritium at the 4 position, we converted such tritiated hydroxyproline to the corresponding N-carbobenzoxy derivative and then oxidized this derivative with chromic acid to N-carbobenzoxy-4-ketoproline according to the procedure of Patchett and Witkop(29). In most of these experiments very little tritiated water was formed although some tritiated water was detected in several experiments, the small amount formed could logically be attributed to adventitious oxidative reactions or perhaps to enolization of ketoproline. The evidence was therefore consistent with the absence of tritium at carbon atom 4 of the isolated hydroxyproline. 

Ebert and Prockop (8) carried out similar studies with 3,4-triti-ated proline in chick embryos, and reported ratios of 0.73 and 0.74. Information supplied by Prockop (32) indicates that this material was from a batch (New England Nuclear Corp.) different from those used by us. They converted the isolated hydroxyproline to pyrrole and found ratios of the H3/C14 values for pyrrole to hydroxyproline of 0.61 and 0.64 (these values were corrected for loss of carboxyl C14, assuming random labeling). We have recently converted the H3-hydroxyproline obtained in our experiments with the new batch of 3,4-tritiated proline to pyrrole (32), and obtained values of 0.70 and 0.73. However, conversion of this hydroxyproline to N-carbobenzoxy-4-ketoproline did not lead to a significant decrease in specific activity, suggesting that little tritium was present at carbon atom 4 of the isolated hydroxyproline. 

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See also in sourсe #XX -- [ ]

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