Preliminary characterization and physical properties of pyridoxal oxidase activity from Drosophila melanogaster

Summary a method of extracting pyridoxal oxidase (PO) activity from D. melanogaster adults is described. in crude extracts, this method allows the activity to remain stable for an extended period of time so that subsequent work on the enzyme can be carried out. The extraction procedure, the constituents of the buffer, and the assay conditions are given. Under these conditions, there is an increase, in specific activity of PO during the first 4 to 8 h following extraction when the extract is held at 4° C. Optimum pH, substrate concentration, and ionic strength are given. In all of these cases the maximum activity points are not chosen since at those values, the lability of the activity is increased. Enzyme activity is also increased by short periods at 55°C. The basis for the increased activity, either upon heating or upon standing at 4°C, is not understood. These and other results are discussed considering the possibility that the structural loci for pyridoxal oxidase and aldehyde oxidase might have arisen as a duplication from an ancestral gene.