Association of lignifying enzymes in shell synthesis of oil palm fruit (Elaeis guineensis--dura variety).

Scanning electron microscopic (SEM) observation demonstrates the differentiation of mesocarp and endocarp tissues and their lignified nature in dura fruits at 8 weeks after pollination (WAP). During shell formation, the endocarp cells become lignified to a hard shell while the mesocarp tissue remains cellular and fibrous. A transition zone made up of fibrous units was also visible beneath the shell. The soluble phenols of mesocarp and endocarp tissues at their developmental stage was analyzed using Reverse phase high performance liquid chromatography (RP-HPLC). The appearance of ferulic acid at 4 WAP and its absence at 8 WAP indicates the role of ferulic acid in lignin synthesis. The HPLC data was supported by the lignin concentration. To ascertain the biochemical relationship of lignin pathway enzymes, phenylalanine ammonia lyase (PAL), cinnamyl alcohol-NADPH-dehydrogenase (CAD) and peroxidase (POD) with shell synthesis, the activities of these enzymes and lignin content were assessed during development of the shell between 4 and 8 WAP. The three enzymes, PAL, CAD and POD expressed high level of activity in the mesocarp and endocarp at 4 WAP. At 8 WAP a sharp decline in activity was observed in the endocarp whereas the mesocarp showed a moderate reduction. This variation is an indication of the role of these enzymes in shell formation.

A cysteine protease of Dieffenbachia maculata.

Plants of the genus Dieffenbachia, very popular as indoor ornamental plants, are known for their toxic as well as therapeutic properties. Their toxic manifestations have been partly attributed to their proteolytic activity. The work described in the present paper shows that stem leaves and petiole of Dieffenbachia maculata Schott, a commonly grown species, contain significant proteolytic activity, different parts showing different types of protease activities. Stem showed the highest enzyme activity and this protease was purified about 55 fold by solvent precipitation, gel filtration and ion exchange chromatography. The enzyme has a relative molecular mass of 61 kDa as determined by SDS-PAGE and has an optimum pH of 8.0 and optimum temperature of 50 degrees C. Effects of various substrates, inhibitors and activators indicate that the enzyme is a cysteine protease with leucylpeptidase activity.