Plant suspension culture media macromolecules-pectic substances, protein, and peroxidase

Macromolecules secreted into the media by a nondifferentiating suspension culture of tobacco cells were found to be composed of protein and polysaccharide, and to account for the viscosity of the media. The concentration, composition, and viscosity of these macromolecules changed significantly with the age of the culture and growth temperature. The concentration changed from 0.02 mg/ml in newly inoculated cultures to over 1 mg/ml in older cultures. The macromolecules contained from 6 to 18% protein and 3 to 4 mumoles hydroxy-proline/mg nitrogen, more than 20 times the level found in whole cells. The macromolecules contained 5 to 25% pectic substances whose carboxyl groups were either methyl esterified or combined with calcium. Arabinose, xylose, glucose, galactose, and mannose were identified in acid hydrolysates of the macromolecules. Peroxidase activity of the macromolecules increased as cultures became older. Peroxidase isoenzyme patterns changed with culture age and growth temperature. The relation of the macromolecules to cell walls and intercellular substances is discussed.