Arabidopsis thaliana NADP-malic enzyme isoforms: high degree of identity but clearly distinct properties

Arabidopsis thaliana NADP-malic enzyme isoforms: high degree of identity but clearly distinct... The Arabidopsis thaliana genome contains four NADP-malic enzymes genes (NADP-ME1-4). NADP-ME4 is localized to plastids whereas the other isoforms are cytosolic. NADP-ME2 and 4 are constitutively expressed, while NADP-ME1 is restricted to secondary roots and NADP-ME3 to trichomes and pollen. Although the four isoforms share remarkably high degree of identity (75–90%), recombinant NADP-ME1 through 4 show distinct kinetic properties, both in the forward (malate oxidative decarboxylation) and reverse (pyruvate reductive carboxylation) reactions. The four isoforms behave differently in terms of reversibility, with NADP-ME2 presenting the highest reverse catalytic efficiency. When analyzing the activity of each isoform in the presence of metabolic effectors, NADP-ME2 was the most highly regulated isoform, especially in its activation by certain effectors. Several metabolites modulate both the forward and reverse reactions, exhibiting dual effects in some cases. Therefore, pyruvate reductive carboxylation may be relevant in vivo, especially in some cellular compartments and conditions. In order to identify residues or segments of the NADP-ME primary structure that could be involved in the differences among the isoforms, NADP-ME2 mutants and deletions were analysed. The results obtained show that Arg115 is involved in fumarate activation, while the amino-terminal part is critical for aspartate and CoA activation, as well as for the reverse reaction. As a whole, these studies show that minimal changes in the primary structure are responsible for the different kinetic behaviour of each AtNADP-ME isoform. In this way, the co-expression of some isoforms in the same cellular compartment would not imply redundancy but represents specificity of function. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Plant Molecular Biology Springer Journals

Arabidopsis thaliana NADP-malic enzyme isoforms: high degree of identity but clearly distinct properties

Loading next page...
 
/lp/springer_journal/arabidopsis-thaliana-nadp-malic-enzyme-isoforms-high-degree-of-0GnFwAQXz2
Publisher
Springer Netherlands
Copyright
Copyright © 2008 by Springer Science+Business Media B.V.
Subject
Life Sciences; Plant Pathology; Biochemistry, general; Plant Sciences
ISSN
0167-4412
eISSN
1573-5028
D.O.I.
10.1007/s11103-008-9313-9
Publisher site
See Article on Publisher Site

Abstract

The Arabidopsis thaliana genome contains four NADP-malic enzymes genes (NADP-ME1-4). NADP-ME4 is localized to plastids whereas the other isoforms are cytosolic. NADP-ME2 and 4 are constitutively expressed, while NADP-ME1 is restricted to secondary roots and NADP-ME3 to trichomes and pollen. Although the four isoforms share remarkably high degree of identity (75–90%), recombinant NADP-ME1 through 4 show distinct kinetic properties, both in the forward (malate oxidative decarboxylation) and reverse (pyruvate reductive carboxylation) reactions. The four isoforms behave differently in terms of reversibility, with NADP-ME2 presenting the highest reverse catalytic efficiency. When analyzing the activity of each isoform in the presence of metabolic effectors, NADP-ME2 was the most highly regulated isoform, especially in its activation by certain effectors. Several metabolites modulate both the forward and reverse reactions, exhibiting dual effects in some cases. Therefore, pyruvate reductive carboxylation may be relevant in vivo, especially in some cellular compartments and conditions. In order to identify residues or segments of the NADP-ME primary structure that could be involved in the differences among the isoforms, NADP-ME2 mutants and deletions were analysed. The results obtained show that Arg115 is involved in fumarate activation, while the amino-terminal part is critical for aspartate and CoA activation, as well as for the reverse reaction. As a whole, these studies show that minimal changes in the primary structure are responsible for the different kinetic behaviour of each AtNADP-ME isoform. In this way, the co-expression of some isoforms in the same cellular compartment would not imply redundancy but represents specificity of function.

Journal

Plant Molecular BiologySpringer Journals

Published: Feb 21, 2008

References

You’re reading a free preview. Subscribe to read the entire article.


DeepDyve is your
personal research library

It’s your single place to instantly
discover and read the research
that matters to you.

Enjoy affordable access to
over 18 million articles from more than
15,000 peer-reviewed journals.

All for just $49/month

Explore the DeepDyve Library

Search

Query the DeepDyve database, plus search all of PubMed and Google Scholar seamlessly

Organize

Save any article or search result from DeepDyve, PubMed, and Google Scholar... all in one place.

Access

Get unlimited, online access to over 18 million full-text articles from more than 15,000 scientific journals.

Your journals are on DeepDyve

Read from thousands of the leading scholarly journals from SpringerNature, Elsevier, Wiley-Blackwell, Oxford University Press and more.

All the latest content is available, no embargo periods.

See the journals in your area

DeepDyve

Freelancer

DeepDyve

Pro

Price

FREE

$49/month
$360/year

Save searches from
Google Scholar,
PubMed

Create lists to
organize your research

Export lists, citations

Read DeepDyve articles

Abstract access only

Unlimited access to over
18 million full-text articles

Print

20 pages / month

PDF Discount

20% off