| Abstrakt: |
A small amount of cytoplasmic β-1,4-glucan, which might be involved in the synthesis of cellulose in the cell wall, was found in the homogenate prepared from the hypocotyls of seedlings of Phaseolus aureus. Upon hydrolysis by cellulase of the 20,000�g pellet from the cytoplasmic fraction of segments incubated in a [14C]-glucose solution, [14C]-cellobiose was produced, with specific radioactivities 3 to 10 times greater than those of the cellobiose from cellulose in the cell wall at various incubation periods. The incoporation of radioactivity from [14C]-glucose into this cytoplasmic β-1,4-glucan was therefore faster than that into cellulose constituting the cell wall. Hence, it seemed that the former β-1,4-glucan could be turned over. To examine whether the- cytoplasmic β-1,4-glucan is carried by some subcellular components, cytoplasmic β-1,4-glucan in the cell was fractionated by differential centrifugation, two enzyme activities being measured as the markers of subcellular components. The distribution of β-1,4-glucan was similar to that of UDPG-glucosyltransferase activity but not to that of IDP-ase activity. The result suggests that the cytoplasmic β-1,4-glucan has some relation to plasma membranes. Coumarin, known as a specific inhibitor for the biosynthesis of cellulose in plant cells, was shown to inhibit the incorporation of radiocarbon from [14C]-glucose into cytoplasmic β-1,4-glucan to the same extent as that into cellulose in the cell wall of the hypocotyls. |
