Apparent inhibition of. beta. -fructosidase secretion by tunicamycin may be explained by breakdown of the unglycosylated protein during secretion. [Daucus carota]

Journal Article · Wed Mar 01 00:00:00 EST 1989 · Plant Physiology; (USA)

DOI:https://doi.org/10.1104/pp.89.3.845· OSTI ID:5025810

Faye, L ^[1]; Chrispeels, M J ^[2]

---

1. Univ. de Rouen, Mont Saint Aignan (France)
2. Univ. of California, San Diego (USA)

Suspension-cultured carrot (Daucus carota) cells synthesize and secrete {beta}-fructosidase, a glycoprotein with asparagine-linked glycans. Treatment of the cells with tunicamycin completely inhibits the apparent secretion of {beta}-fructosidase as measured by the accumulation of the {sup 35}S-labelled protein in the cell wall or the culture medium. In the past, such a result has been interpreted as an inhibition of secretion by tunicamycin, but we suggest another explanation based on the following results. In the presence of tunicamycin, unglycosylated {beta}-fructosidase is synthesized and is associated with an endoplasmic-reticulum-rich microsomal fraction. Pulse-chase experiments show that the unglycosylated {beta}-fructosidase does not remain in the cells and appears to be secreted in the same way as glycosylated {beta}-fructosidase; however, no radioactive, unglycosylated {beta}-fructosidase accumulates extracellularly (cell wall or medium). Protoplasts obtained from carrot cells secrete {beta}-fructosidase protein and activity, and treatment of the protoplasts with tunicamycin results in the synthesis of unglycosylated {beta}-fructosidase. In the presence of tunicamycin, there is no accumulation of {beta}-fructosidase activity or unglycosylated {beta}-fructosidase polypeptide in the protoplast incubation medium. These results are consistent with the interpretation that the glycans of {beta}-fructosidase are necessary for its stability, and that in these suspension-cultured cells, the unglycosylated enzyme is degraded during the last stage(s) of secretion, or immediately after its arrival in the wall.

• OSTI ID: 5025810
• Journal Information: Plant Physiology; (USA), Vol. 89:3; ISSN 0032-0889
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
ANTIBIOTICS
BIOLOGICAL EFFECTS
GLYCOPROTEINS
BIOCHEMICAL REACTION KINETICS
PLANT CELLS
PHYSIOLOGY
CARROTS
ENZYME ACTIVITY
LABELLED COMPOUNDS
STABILITY
SULFUR 35
TRACER TECHNIQUES
ANTI-INFECTIVE AGENTS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
DAYS LIVING RADIOISOTOPES
DRUGS
EVEN-ODD NUCLEI
FOOD
ISOTOPE APPLICATIONS
ISOTOPES
KINETICS
LIGHT NUCLEI
MAGNOLIOPHYTA
MAGNOLIOPSIDA
NUCLEI
ORGANIC COMPOUNDS
PLANTS
PROTEINS
RADIOISOTOPES
REACTION KINETICS
SULFUR ISOTOPES
VEGETABLES
551001* - Physiological Systems- Tracer Techniques