| Popis: |
The biosynthesis in vitro of tetrahymanol (II) from squalene (I) by enzyme preparations of the protozoan Tetrahymena pyriformis is described. The enzyme system involved has been obtained in a soluble, cell-free, lipid-free form, and remains active after freeze-drying. As with the live protozoa, the biosynthesis of tetrahymanol in vitro does not proceed via the intermediacy of 2,3-oxidosqualene; instead a nonoxidative, enzymatic cyclization of squalene occurs. This is an anaerobic process, and has been shown by isotopic labeling experiments with D2O and H218O to result in the acquisition of a hydrogen atom from the medium, presumably at C-3 of tetrahymanol and an oxygen atom from the medium at C-21 of tetrahymanol. The biogenetic implications of these findings are discussed. |
