Plant Physiol.
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Plant Physiology 59:673-679 (1977)
© 1977 American Society of Plant Biologists

This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in Web of Science
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via CrossRef
Right arrow Citing Articles via Web of Science (31)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Bryan, J. K.
Right arrow Articles by Matthews, B. F.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Bryan, J. K.
Right arrow Articles by Matthews, B. F.
Agricola
Right arrow Articles by Bryan, J. K.
Right arrow Articles by Matthews, B. F.
Articles

Changes in Enzyme Regulation during Growth of Maize

III. Intracellular Localization of Homoserine Dehydrogenase in Chloroplasts 1

John K. Bryan, Eve A. Lissik and Benjamin F. Matthews2

a Biological Research Laboratories, Syracuse University, Syracuse, New York 13210

Extracts of leaf tissue of Zea mays L. seedlings were fractionated on nonlinear sucrose gradients to separate subcellular organelles. Homoserine dehydrogenase (EC 1.1.1.3) was identified in those fractions containing intact chloroplasts, as judged by the presence of chlorophyll and triosephosphate isomerase activity. Neither enzyme activity was detected in fractions containing ruptured chloroplasts, mitochondria, or microbodies. Quantitative measurements of enzyme activity and chlorophyll, and electron microscopic analysis of plastid preparations support the conclusion that maize mesophyll chloroplasts contain a significant fraction of the total cellular content of homoserine dehydrogenase.

A survey of representative kinetic, regulatory, and physical properties did not reveal any significant differences between enzyme released from isolated, undamaged chloroplasts and that obtained from soluble cellular fractions.

Examination of enzyme prepared from chloroplasts of different age seedlings indicated that the sensitivity of homoserine dehydrogenase to inhibition by the feedback modifier L-threonine was progressively diminished during growth of the plants. This systematic change in regulatory properties of the enzyme occurred to the same extent for the enzymes obtained from chloroplasts and soluble fractions.

2 A portion of this work was taken from a dissertation submitted by B. F. M. to the Graduate School of Syracuse University in partial fulfillment of the requirements for the Ph.D. degree. Present address: Department of Agronomy, The University of Illinois, Champaign-Urbana, Ill.

1 This research was supported by National Science Foundation Grant PCM71-01093 and a grant from the Syracuse University Senate Research Fund.






HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
ASPB Publications PLANT PHYSIOLOGY® THE PLANT CELL
Copyright © 1977 by the American Society of Plant Biologists