Biochemical studies of matured xylem of Crytomeria japonica: Attempts to detect the enzymes involved in the biosyntheses of the heartwood extractives
2005
Imai, T.(Nagoya Univ. (Japan)) | Ito, E. | Fukushima, K.
Many biochemical actions occur in mature tree xylem after cell differentiation is completed in the differentiating xylem. However, biochemical studies of the mature xylem are scarce. One of the most remarkable actions of mature tree xylem is the process of changing sapwood to heartwood, so-called heartwood formation. Generally, heartwood contains particular organic solvent extractable substances called heartwood extractives. In this study we attempted to investigate the biochemical abilities of mature sugi xylem from the perspective of heartwood extractive formation. First, frozen wood powders were prepared from various parts of the xylem. These powders were subjected to buffer extraction, and crude protein extracts were obtained by ammonium sulfate precipitation. The protein contents were determined colorimetrically, and no increase of protein content corresponding to formation of the heartwood extractives in the intermediate wood was found. Protein constitutions were also examined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and no alteration of the constitutions corresponding to formation of the extractives in the intermediate wood was found. Conversely, the activity of phenylalanine ammonia-lyase, an enzyme that would be involved in the biosyntheses of sugi heartwood extractives, was determined by gas chromatography-mass spectrometry and was significantly increased in the intermediate wood. Consequently, frozen wood powder is useful for biochemical studies of mature tree xylem, and by using the powder detection of the bioability of mature xylem concerning formation of sugi heartwood extractives was achieved.
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