Porosity of the cell wall as related to the Secretion of proteolytic enzymes in N. crassa

Secretion of proteolytic enzym

Function of Lysosomes and Lysosomal Enzymes in the Senescing Corolla of the Morning Glory (Ipomoea purpurea)

The rapid senescence of the Ipomoea corolla is characterized by the breakdown of protein and nucleic acids. At the onset of wilting the activities of deoxyribonuclease (DNase), ribonuclease (RNase), and β-glucosidase are increased dramatically, while other hydrolytic activities such as the actions of protease, aminopeptidase, α-glucosidase, phosphatase, esterase, and α-amylase are only slightly changed. Isolated corolla discs show a course of senescence similar to that of the intact organ. When floating on solutions of cycloheximide the activities of DNase, RNase, and β-glucosidase do not increase. Actinomycin D inhibits the increase in RNase activity. It is concluded that protein synthesis is a prerequisite for the changes in these enzyme activities in the senescing corolla. The function of the lysosomal compartment in the process of senescence is illustrated by electron micrographs showing the autophagic activity of vacuoles. The last phase of senescence is characterized by the breakdown of the tonoplast and complete digestion of the cytoplasmic constituents in the autolysing cell

Glycosidases in pear pollen tube development

During the in vitro germination of pear pollen, several hydrolases were released into the medium. They were apparently eluted from the pollen grain, since the activity was the same when germination was inhibited. These enzymes, once released, had no role in tube growth, since resuspension of pollen in fresh medium after 1.5 hr of incubation did not result in a change of the subsequent tube growth. Homogenates of the pollen suspension at different stages of development showed no significant changes in phosphatase, β-glucosidase, or β-galactosidase activity. However, patent β-glucosidase activity measured directly in suspensions of intact pollen did increase after germination in proportion to tube wall development. Nojirimycin, a specific inhibitor of glucosidases, reduced this β-glucosidase activity by 75% at 10−5M and significantly reduced growth rate at 10−4

A Synthetic Chloride Channel Restores Chloride Conductance in Human Cystic Fibrosis Epithelial Cells

Mutations in the gene-encoding cystic fibrosis transmembrane conductance regulator (CFTR) cause defective transepithelial transport of chloride (Cl−) ions and fluid, thereby becoming responsible for the onset of cystic fibrosis (CF). One strategy to reduce the pathophysiology associated with CF is to increase Cl− transport through alternative pathways. In this paper, we demonstrate that a small synthetic molecule which forms Cl− channels to mediate Cl− transport across lipid bilayer membranes is capable of restoring Cl− permeability in human CF epithelial cells; as a result, it has the potential to become a lead compound for the treatment of human diseases associated with Cl− channel dysfunction

Function of Lysosomes and Lysosomal Enzymes in the Senescing Corolla of the Morning Glory (Ipomoea purpurea)

ISSN:1460-2431ISSN:0022-095

Glycosidases in pear pollen tube development

ISSN:0032-0781ISSN:1471-905

Cell-wall-bound lytic activity in Chlorella fusca: function and characterization of an endo-mannanase

A cell-wall-degrading activity was solubilized from young cells and from mother cell walls of Chlorella fusca by treatment with LiCl. The cytoplasmic enzyme hexokinase was not detectable in these extracts. The LiCl-solubilized activity increased in the cell cycle parallel to the release of autospores. The enzyme was purified on a chromatofocusing column followed by gel filtration. Sodium dodecyl sulfate/polyacryl amide gel electrophoresis of the purified enzyme revealed a molecular weight of 44 kDa, whereas gel filtration indicated a molecular weight of 25 kDa. Cell-wall-lytic activity and beta-1,4-mannanase activity coeluted in gel filtration and were separated from beta-d-fucosidase activity. The enzyme degraded isolated cell walls and ivory nut mannan primarily to oligosaccharides with an estimated degree of polymerization gE6. The soluble degradation products of the cell wall consisted of 92–96% mannose and 4–8% glucose. It is concluded that the cell-wall-lytic activity is caused by an endo-mannanase. In vivo, this enzyme probably degrades the mother cell wall and, after autospore release, remains bound to it as well as to the surface of the daughter cells by ionic forces. The identity of this bound enzyme with a soluble wall-degrading enzyme previously obtained from mother cells is discussed