Multiple Forms of Invertase in Developing Oat Internodes

Abstract

Three different invertases are found in the developing internodes of oat (Avena sativa cv. Victory). Two soluble invertases (I and II)

The Acid Invertases of the Developing Third Leaf of Oat

“…Pollock and Lloyd (1977) consider the insoluble activity of homogenates of darnel leaves to represent extracellular acid invertase as the ratio of release of reducing sugar before and after treatment with ethyl acetate (to rupture cell membranes: Bacon et al, 1965) was similar to the ratio of insoluble to soluble activity in tissue homogenates of leaves of the same age. A range of buffers of differing pH and ionic strength did not release the particulate invertase prepared from oat internodes (Jones and Kaufman, 1975). The failure to solubilize particulate activity from oat internodes may have resulted from the method of preparation of this fraction.…”

“…The failure to solubilize particulate activity from oat internodes may have resulted from the method of preparation of this fraction. Although the oat internodes were originally extracted in a buffered medium, the subsequent purification of the particulate acid invertase was via sequential treatments with acetone and diethyl ether, followed by desiccation (Jones and Kaufman, 1975). This method of preparation appears to give a particulate acid invertase from oats that has a different solubility from that prepared in this study.…”

“…The association of high activity of soluble acid invertase with, in general, high levels of reducing sugar and low levels of sucrose has been noted in several tissues undergoing rapid cell division and expansion, e.g. elongating roots (Ricardo and ap Rees, 1970;Lyne and ap Rees, 1971;Macleod and Francis, 1977) and stem internodes (Hatch and Glaziou, 1963;Jones and Kaufman, 1975). The tip ofthe lamina represents the oldest region of the leaf (Begg and Wright, 1962;Langer, 1972) and, although direct experimental evidence from radioactive tracer studies is lacking, as it is the first part of the lamina exposed to an environment favourable for photosynthesis, it most probably ceases to import photosynthetic assimilate soon after emergence.…”

“…One enzyme in particular, acid invertase (/?-D-fructofuranoside fructohydrolase, EC 3.2.1.26), has been proposed to play a key role in the utilization of sucrose in sinks (ap Rees, 1974). In several higher plant tissues, including leaves, acid invertase may be located both inside and outside the plasmalemma (Weatherley, 1953;Bacon, MacDonald and Knight, 1965 ;Brovchenko, 1970) and, in tissue homogenates, the enzyme may be present in both soluble and insoluble fractions (Archbold, 1940;Jones and Kaufman, 1975;Pollock and Lloyd, 1977). The degree of binding of invertase to the cell wall in vivo is difficult to assess and several techniques, in particular extraction in buffers of high pH and ionic strength, can solubilize considerable quantities of acid invertase from the cell wall (Ricardo and ap Rees, 1970;Parr and Edelman, 1975).…”

The Acid Invertases of the Developing Third Leaf of Oat

“…In some cases, the control exerted by one or more of these factors results in differential changes in the activity of isoenzymic forms of acid invertase, e.g. in endosperm of maize seed (Jaynes and Nelson, 1971a,b), elongating internodes of oat (Jones and Kaufman, 1975) and in wounded sweet potato tissue Uritani, 1974, 1977).…”