The loss of carbon-20 in C19-gibberellin biosynthesis in a cell-free system fromPisum sativumL.

✍ Scribed by Y. Kamiya; N. Takahashi; J. E. Graebe

• Publisher: Springer-Verlag
• Year: 1986
• Tongue: English
• Weight: 480 KB
• Volume: 169
• Category: Article
• ISSN: 0032-0935
• DOI: 10.1007/bf00392102

✦ Synopsis

The fate of the carbon-20 atom in gibberellin (GA) biosynthesis was studied in a cell-free system from Pisum sativum. This carbon atom is lost at the aldehyde stage of oxidation when C2o-GAs are converted to C19-GAs. Gibberellin A~2 labeled with 14C at C-20 was prepared from [3"-~4C]mevalonic acid with a cell-free system from Cucurbita maxima and incubated with the pea system. Analysis of the gas and aqueous phases showed that ~4CO2 was formed at the same rate and in nearly equivalent amounts as ~4C-labeled C19-GAs whereas [14C]formic acid and [14C]formaldehyde were not detectable. The possibility that C-20 had been lost as formic acid which had then been converted to COz was investigated by control incubations with [~4C]formic acid. The rate of release of 14CO2 from [a4C]formic acid was only one fiftieth of the rate of 14CO2 release from [14C]GA12 as the substrate. We conclude that in the formation of C~9-GAs from C2o-GAs, the C-20 is removed directly as CO2.