Seed Germination Studies. III. Properties of a Cell-free Amino Acid Incorporating System From Pea Cotyledons; Possible Origin of Cotyledonary α-Amylase

Abstract

Abstract. Pea cotyledonary a-amylase increases dramaticallv both in specific activity and total activity between days 7 to 10 when germination occurs in the dark. This enzymatic activity does not seem to appear as a consequence of release or formation of an activator, removal of an inhibitor, dissociation of an inactive amylase complex, or proteolytic decomposition of a zymogen precursor. The possibility remains that the a-amylase is newly synthesized during germination. The preparation and properties of a cell-free protein-synthesizing system from germinating pea cotyledons is described; polyuridylic acid must be added for L-phenylalanine incorporation. Active microsomal preparations can be obtained from cotyledons germinated 10 days.Seed germination is frequently accompanied bv marked increases in the level of activity of certain enzymes (3,4,12,17, 23,32). It has been noted that these often dramatic increases in biocatalytic activity are not necessarily associated only with those parts of the seedling that are actively growing. Rather. the same phenomenon is also observed in the storage tissues of the endosperm or cotyledon (4, 17, 32).We showed in previous reports '(25, 26) that a number of enzvmes required for the degradation of seed carbohydrate reserves are present in the cotvledon of the germinating pea, and at least 2 of these enzymes, an a-amylase and a phosphorylase. increase manyfold in total activity during the time period of germination. Since, in many instances, the cells of plant storage organs neither grow nor divide, the question arises as to what the origin of such new enzymatic activities mlay be. Other workers dernonstrated that activation of latent enzyme occurs in the case of the ,-amylase of wheat (21,22), zymogen activation causes an increase in acid phosphatase and isocitritase activiti-es of a variety of seeds (17), whereas isocitritase (6,10). malate synthetase (10), tyramine methylpherase (12), and barley a-amvlase (5, 28) increase in activity as a result of de novo enzyme synthesis.We report here studies which show that cotvledonary a-amylase of peas most likely does not appear during germination as a consequence of the formation or release of a specific activator, the removal of an inhibitor, or the activation of a latent form (or zymogen precursor) of the enzyme. The possibility that the enzyme is newly synthesized is not eliminated.A cell-free protein-synthesizing system from the cotyledons of germinating peas has been prepared and its properties determined. A catalytically-active microsomal fraction can be prepared from cotyledons at a time during germination when the level of oa-amvlase activity is rapidlv increasilng.

Influence of Cotyledons upon α-Amylase Activity in Pea Embryonic Axes

“…Although a-amylase activity was low in cotyledons of ungerminated pea, it increased 5-to 10-fold during the 2nd or 3rd week of seedling growth (5,16,26,27,29,32, 37). The increased activity was associated with a rapid loss of starch in peas (1,16,26) and lentils (30).…”

The Growth Response and Digestive Enzyme Activity of Juvenile African Catfish (Clarias gariepinus) Exposed to Artificial Light at Night (ALAN) Spectral

“…The amount of reducing sugar produced was calculated. A standard curve for maltose was used to calculate the amount of reducing sugar that was produced (Swain and Dekker, 1966).…”

Changes in Nucleic Acid Fractions of Seed Components of Red Pine (Pinus resinosa Ait.) during Germination

“…Although in general, nucleic acids quantitatively increase in embryos during germination, patterns of nucleic acid metabolism and protein synthesis show differences between species, and even between seed groups of the same species (14). Patterns of nucleic acid metabolism in storage tissues such as endosperm and cotyledons vary greatly among different species (7,12,19,22,26). Although cotyledons of many angiosperms play a role as storage tissue, cotyledons in red pine differentiate and function as an important photosynthetic apparatus in early stages of seedling development (24,25).…”