A biochemical comparison between latex from Carica candamarcensis and C. papaya.

1. A group of plant proteinases is present mainly in the unripe fruit of the papaya tree (Carica papaya), which is a member of the genus Carica. C. candamarcensis is another species that belongs to this group. Its latex contains several proteinases displaying high proteolytic activity. 2. We used several electrophoretic techniques to compare the protein composition of the latex from the two species. Acid electrophoresis followed by staining or Western blot revealed a total of 17 proteins in C. candamarcensis and 7 proteins in C. papaya. Some of the proteins observed in C. papaya have been previously reported in the literature. 3. Electrophoresis on denaturing gels, followed by staining or Western blot revealed the presence of 14 proteins in C. candamarcensis and 6 proteins in C. papaya. Non-equilibrium isoelectrofocusing of the latex from both species showed a larger array of proteins in C. candamarcensis. The analysis of esterase and proteolytic activities on gel fractions after electrophoresis revealed the presence of distinct areas presenting enzyme activity. Some proteins detected in C. candamarcensis have different mobilities when compared with proteins from C. papaya. 4. These results support the view that latex from C. candamarcensis contains a wider diversity of proteins compared to C. papaya, and that some of the proteins not in C. papaya present esterase and proteolytic activity.