384 



The Philippine Journal of Science 



191S 



cent sucrose gradually deteriorated until after two weeks they 

 contained only 0.5 per cent. The Brix decreased correspondingly, 

 while the small amounts of invert sugar originally present com- 

 pletely disappeared. A careful bacteriological examination by 

 E. L. Walker of the Bureau of Science showed these samples to 

 be practically sterile. The only plausible explanation of this 

 peculiar behavior seemed to be based upon the presence of enzyme 

 activity. We have found that the nipa palm actually does elabor- 

 ate a very active enzyme of the peroxidase type. Slices of the 

 plant immediately give a dark blue with tincture of guaiacum and 

 hydrogen peroxide and characteristic colors with all the specific 

 tests for this class of enzymes. The speed with which these 

 colors are developed indicates an activity of unusual magnitude. 

 The peroxidase is distributed throughout the entire palm, being 

 present in slight amount in the midrib of the leaf and very 

 strong in the immature fruit. The juice secreted by long flower 

 stalks producing a free flow of sap gave negative tests for the 

 presence of this enzyme, while tuba, from short stems approach- 

 ing the end of the sap flow, always gave strongly positive tests. 

 It is evident that the character of the juice changes as the season 

 of flow advances, probably due to the varying requirements of 

 the maturing fruit. A careful series of experiments proved 

 beyond doubt that some enzyme capable of destroying both su- 

 crose and invert sugar is present in the nipa palm. It is active 

 in neutral or alkaline solution, but is killed by inorganic acids 

 or heat. Solutions of pure sucrose, both neutral and alkaline 

 with lime, were treated with thin slices of palm tissue containing 

 the enzyme. These solutions were polarized, and the Brix was 

 determined at regular intervals. The sucrose content and den- 

 sity decreased regularly, both in the neutral and alkaline solu- 

 tions. Tables IV and V show the rate at which sucrose was 

 destroyed in two representative experiments. 



Table IV. — Enzyme destruction of sucrose in neutral solution. 



Time. 



Sucrose. 



Brix. 



Present. 



De- 

 stroyed. 



Hrs. 





 12 

 24 

 86 

 48 

 60 

 72 



Per cent. 

 14.40 

 14. 15 

 13.90 

 13.70 

 13.40 

 13.20 

 13.00 



Per cent. 

 



1.07 

 3.47 

 4.86 

 6.94 

 8.33 

 9.72 



14.5 

 14.4 



14.2 



14.0 



