This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Robinson, N. L. Articles by Preiss, J. Search for Related Content PubMed PubMed Citation Articles by Robinson, N. L. Articles by Preiss, J. Agricola Articles by Robinson, N. L. Articles by Preiss, J.

Metabolism and Enzymology

Localization of Carbohydrate Metabolizing Enzymes in Guard Cells of Commelina communis¹

Department of Biochemistry and Biophysics, University of California, Davis, California 95616

The localization of enzymes involved in the flow of carbon into and out of starch was determined in guard cells of Commelina communis. The guard cell chloroplasts were separated from the rest of the cellular components by a modification of published microfuge methods. The enzymes of interest were then assayed in the supernatant and chloroplast fractions. The chloroplast yield averaged 75% with 10% cytoplasmic contamination. The enzymes involved in starch biosynthesis, ADPglucose pyrophosphorylase, starch synthase, and branching enzyme, are located exclusively in the chloroplast fraction. The enzymes involved in starch degradation show a more complex distribution. Phosphorylase is located in both the supernatant and chloroplast fraction, 50% in each fraction. Most of the amylase and debranching enzyme activity is present in the supernatant (70%) fraction. The majority of the rest of the enzymes involved in the degradation of starch to malate and synthesis of starch from a hexose precursor were also investigated. All of the enzymes were present in the chloroplast except for hexokinase and phosphofructokinase. The inability to assay these enzymes could possibly have been due to the lack of or low activity of the enzymes or to nonoptimal assay conditions.

³ Present address: Department of Biochemistry, Michigan State University, East Lansing, MI 48824.

¹ Supported in part by a National Science Foundation grant PCM82-0570.

This article has been cited by other articles:

				E. Baroja-Fernandez, F. J. Munoz, A. Zandueta-Criado, M. T. Moran-Zorzano, A. M. Viale, N. Alonso-Casajus, and J. Pozueta-Romero Most of ADP{middle dot}glucose linked to starch biosynthesis occurs outside the chloroplast in source leaves PNAS, August 31, 2004; 101(35): 13080 - 13085. [Abstract] [Full Text] [PDF]

				D. M. Beckles, A. M. Smith, and T. ap Rees A Cytosolic ADP-Glucose Pyrophosphorylase Is a Feature of Graminaceous Endosperms, But Not of Other Starch-Storing Organs Plant Physiology, February 1, 2001; 125(2): 818 - 827. [Abstract] [Full Text]

				B.-Y. Chen, Y. Wang, and H. W. Janes ADP-Glucose Pyrophosphorylase Is Localized to Both the Cytoplasm and Plastids in Developing Pericarp of Tomato Fruit Plant Physiology, January 1, 1998; 116(1): 101 - 106. [Abstract] [Full Text]

				D. M. Stark, K. P. Timmerman, G. F. Barry, J. Preiss, and G. M. Kishore Regulation of the Amount of Starch in Plant Tissues by ADP Glucose Pyrophosphorylase Science, October 9, 1992; 258(5080): 287 - 292. [Abstract] [PDF]