+ Site Statistics
+ Search Articles
+ Subscribe to Site Feeds
EurekaMag Most Shared ContentMost Shared
EurekaMag PDF Full Text ContentPDF Full Text
+ PDF Full Text
Request PDF Full TextRequest PDF Full Text
+ Follow Us
Follow on FacebookFollow on Facebook
Follow on TwitterFollow on Twitter
Follow on LinkedInFollow on LinkedIn

+ Translate

Differentiation between Several Types of Phosphohydrolases in Light Microsomes of Corn Roots

Differentiation between Several Types of Phosphohydrolases in Light Microsomes of Corn Roots

Plant Physiology 96(4): 1345-1353

The phosphohydrolase activity of a light microsomal fraction isolated from corn roots (Zea mays L. cv LG 55) was investigated. The fraction, which appears to be enriched in endoplasmic reticulum and Golgi membranes, has ATPase and pyrophosphatase activities that hydrolyze ATP and pyrophosphate at an optimum pH of 7.0, with K(m) values of about 160 and 240 micromolar and with V(max) values of about 200 and 50 nanomoles substrate hydrolyzed per milligram protein per minute, respectively. These enzymes differ in their sensitivity to anions and inhibitors. The ATPase is stimulated by sulfate anions, whereas pyrophosphatase is inhibited by molybdate. Furthermore, the simultaneous addition of ATP and pyrophosphate to the reaction medium increases phosphohydrolysis, suggesting that separate enzymes are operating in the membranes. We also observed that pyrophosphate competitively inhibits the ATPase, whereas ATP has no significant effect on the pyrophosphatase. On the other hand, we observed a detergent-stimulated, molybdate-insensitive inosine diphosphatase activity which, in the native state, hydrolyzes inosine diphosphate with a K(m) of about 700 micromolar and a V(max) of about 450 nanomoles inosine diphosphate hydrolyzed per milligram protein per minute. In the solubilized form, the enzyme appears to be fully active, exhibiting lower K(m) values to hydrolyze inosine diphosphate. Furthermore, we found that native inosine diphosphatase is inhibited either by ATP or pyrophosphate, whereas inosine diphosphate inhibits the ATPase, but has no significant effect on the pyrophosphatase. It appears that inosine diphosphate is a positive modulator of the inosine diphosphatase, whereas ATP and pyrophosphate act as negative modulators of this enzyme.

(PDF same-day service: $19.90)

Accession: 002072892

Download citation: RISBibTeXText

PMID: 16668340

DOI: 10.1104/pp.96.4.1345

Related references

ATP- und ADP-phosphohydrolasen in MStuselebermikrosomen JATP- and ADP-phosphohydrolases in mouse liver microsomes. Acta Biol Med Ger: 607-617, 1965

Characterization of different types of atpase activities in microsomes isolated from roots and coleoptiles of zea mays l. Ciencia Biologica Molecular & Cellular Biology 13(1-2): 1-14, 1988

Functional differentiation of the surface cells in corn m roots. Sel'skokhozyaistvennaya Biologiya 6(2): 242-250, 1971

Dynamics of free amino acids in roots of corn grown on different types of soil. Physiology and biochemistry of cultivated plants: (Transl 1971), 2 (2) 139-141, 1970

The dynamics of the free amino acids in the roots of corn m grown on different types of soils. Fiziologiya i Biokhimiya Kul'turnykh Rastenii 2(2): 171-175, 1970

Adenosine triphosphate and adenosine diphosphate phosphohydrolases in liver microsomes of mice. Acta Biologica et Medica Germanica 14(6): 607-617, 1965

Role of various types of corn roots in plant nutrition and their physiological features under irrigation conditions. Fiziol Rast 10(1): 23-30, 1963

Cellular differentiation and proliferation in corn roots grown in microgravity (Biocosmos 1985). Advances in Space Research 6(12): 157-160, 1986

Nitrogen assimilation in roots and leaves of corn seedlings in the dark and under light. Soviet Plant Physiology 38(1, I): 64-70, 1991

Rapid changes in protein phosphorylation associated with light-induced gravity perception in corn roots. Plant Physiology 86: 332-334, 1988

The translocation of assimilates from the leaves into the roots of young corn plants in the light and in darkness. Uch Zap Perm Gos Pedagog Inst 39: 119-122, 1966

The effect of calcium on protein synthesis in light induced gravitropism in corn roots. Plant Physiology (Rockville) 83(4 SUPPL): 19, 1987

Changes in anatomic-morphological structure of corn (Zea mays L.) roots under the influence of flooding and lack of light. Moscow University biological sciences bulletin7(1): 22-28, 1982

The effect of different wavelengths of light on the differentiation of chloroplasts in roots. Periodicum Biologorum 76(1): 54, 1974

Respiration and absorption of phosphorus and potassium by corn roots depending on light of varying spectral composition. Ukr Bot Zh 24(1): 15-20, 1967