ISSN:
1399-3054
Source:
Blackwell Publishing Journal Backfiles 1879-2005
Topics:
Biology
Notes:
The effects of the addition and withdrawal of gibberellic acid (GA3) and Ca2+ on enzyme synthesis and secretion by barley (Hordeum vulgare L. cv. Himalaya) aleurone layers were studied. Incubation of layers in GA3 plus Ca2+ affects the total amount of secreted α-amylase (EC 3.2.1.1) and acid phosphatase (EC 3.1.3.2) by promoting the appearance of different isoenzymic forms of these enzymes. The release of α-amylase isoenzymes 1–4 in response to GA3 plus Ca2+ has a lag of 6 h. When layers are incubated in GA3 alone for 6 h prior to the addition of Ca2+, isoenzymes 1–4 appear in the medium after only 30 min. When the addition of Ca2+ to layers pretreated in GA3 is delayed beyond 12 h, its effectiveness in stimulating the synthesis and release of isoenzymes 3 and 4 is diminished. After 35 h of preincubation in GA3, addition of Ca2+ will not stimulate synthesis of α-amylase isoenzymes 3 and 4. Aleurone layers preincubated for 6 h in GA3 will respond to Ca2+ when the GA3 is withdrawn from the incubation medium by producing α-amylase isoenzymes 1–4. The converse is not the case, however, since layers preincubated in Ca2+ for 6 h will not produce all isoenzymes of α-amylase when subsequently incubated in GA3. The Ca2+-stimulated release of α-amylase from GA3 pre-treated layers is dependent on the time of incubation in Ca2+ and the concentration of the ion. The response to Ca2+ is temperature-dependent, and other divalent cations such as Mg2+ cannot substitute for Ca2+. We conclude that Ca2+ influences α-amylase release by influencing events at the biochemical level.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1111/j.1399-3054.1985.tb02308.x
