Binding of Tomato Pectinesterase and β-Fructofuranosidase to Tomato Cell Wall

Abstract

The cell wall of tomato pericarps prepared with sucrose density gradient centrifugation showed considerable binding capacity to pectinesterase(PE) and β-fructofuranosidase (βFF). The half maximal binding concentration of PE for the cell wall decreased, while the total uronic acid content increased as ripening and senescence developed. Potassium β-indoleacetate (IAA) had no promoting effect on the binding capacity of PE and β-FF to tomato cell wall at least at the concentration range of 10⁻⁸ to 10⁻¹⁰ m. Divalent cations such as calcium ions and magnesium ions at the concentration of 10⁻² m decreased the binding capacity of PE and β-FF to the cell wall by 20%. The PE-saturated cell wall still retained 59% of the binding capacity to β-FF, while the β-FF-saturated cell wall retained 73% of the capacity to PE. It is suggested that PE and β-FF are bound to different sites on the tomato cell wall.