Change search
ReferencesLink to record
Permanent link

Direct link
Preparation of leaf mitochondria and studies on mitochondrial photorespiratory reactions
Umeå University, Faculty of Science and Technology, Department of Plant Physiology.ORCID iD: 0000-0001-5900-7395
1981 (English)Doctoral thesis, monograph (Other academic)
Abstract [en]

A procedure for the preparation of spinach leaf mitochondria was developed. The procedure combines differential centrifugation, partition in dextran- polyethyleneglycol two-phase system and Percoli density gradient centri- fugation. The different steps separate the material mainly according to size, surface properties and density, respectively. No chlorophyll was present in the final mitochondrial preparation and the mitochondria were also markedly enriched relative to peroxisomes and microsomes as esti­mated from the recovery of marker enzymes. The latency of enzyme activities was used to study the apparent intactness of the mitochondrial membranes. These measurements showed that both the inner and outer mitochondrial membranes were more than 90 % intact. The mitochondria were also functionally intact since the coupling between respiration and oxidative phosphorylation was retained.

The purity of the preparation made it possible to study cytochromes from leaf mitochondria. The cytochrome content of stalk and leaf mitochondria was measured in order to compare mitochondria from photosynthesizing and non-photosynthesizing tissue. The measurements were performed by difference spectroscopy both at room temperature and at liquid nitrogen temperature. Qualitatively the cytochrome content in mitochondria from stalks and leaves was identical. Quantiatively leaf mitochondria contained,on a protein basis, only half the amount of the different cytochromes as compared to stalk mitochondria. The relative content of the different cytochromes was, however, similar suggesting that the composition of the respiratory chain was the same.

The photorespiratory conversion of glycine to serine takes place in the mitochondria and involves oxidative decarboxylation of glycine. The ability to oxidize glycine via the respiratory chain was present in spinach leaf mitochondria, but absent in mitochondria prepared from roots, stalks and leaf veins from the same plants. This confirmed the specific localization of the glycine oxidizing activity to photosyntheticaliy active tissue, as suggested by studies with other plant material.

The conversion of glycine to serine is a complex reaction depending on the combined action of two enzymes: glycine decarboxylase and serine hydroxymethyltransferase. The effect of inhibitors on the serine hydroxy­methyl transferase activity and the rate of the glycine bicarbonate exchange reaction associated with glycine decarboxylase was studied. These reactions represent partial steps in the conversion of glycine to serine and the aim was to investigate the site of inhibition for the different inhibitors, namely, isonicotinyl hydrazide (a pyridoxa!phosphate antagonist), amino- acetonitrile, glycinehydroxamate (glycine analogues) and cyanide. The results showed that these inhibitors had a complex pattern of inhibition. The same inhibitor affected more than one site and often with an apparently different mechanism. It was, however, found that aminoacetonitrile at low concentrations specifically inhibited glycine decarboxylase and that cyanide specifically inhibited serine hydroxymethyltransferase.

Place, publisher, year, edition, pages
Umeå: Umeå universitet , 1981. , 29 p.
Keyword [en]
leaf mitochondria, photorespiration, aqueous two-phase system, Percoli gradient, cytochromes, glycine decarboyxlase, serine hydroxymethyltransferase, inhitors of photorespiration
National Category
URN: urn:nbn:se:umu:diva-73362ISBN: 91-7174-078-3OAI: diva2:631106
Available from: 2013-06-20 Created: 2013-06-20 Last updated: 2015-04-29Bibliographically approved

Open Access in DiVA

fulltext(3095 kB)149 downloads
File information
File name FULLTEXT01.pdfFile size 3095 kBChecksum SHA-512
Type fulltextMimetype application/pdf

Search in DiVA

By author/editor
Gardeström, Per
By organisation
Department of Plant Physiology

Search outside of DiVA

GoogleGoogle Scholar
Total: 149 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

Total: 45 hits
ReferencesLink to record
Permanent link

Direct link