Isolation of the bifunctional enzyme lysine 2-oxoglutarate reductase-saccharopine dehydrogenase from Phaseolus vulgaris

Braz. J. Plant Physiol.

Ferreira

et al. 2003

Lysine is an essential amino acid, synthesized in plants in the aspartic acid pathway. The lysine catabolism is performed by the action of two consecutive enzymes, lysine 2-oxoglutarate reductase (LOR) and saccharopine dehydrogenase (SDH). The steady state of lysine is controlled by both, synthesis and catabolism rates, with the final soluble lysine concentration in cereal seeds a direct result of these processes. In the last 40 years, the enzymes involved in lysine biosynthesis have been purified and characterized from some plant species such as carrot, maize, barley, rice, and coix. Recent reports have revealed that lysine degradation might be related to various physiological processes, for instance growth, development and response to environmental changes and stress. The understanding of the regulatory aspects of the lysine biosynthetic and catabolic pathways and manipulation of related enzymes is important for the production of high-lysine plants.

Section: The Purification and Characterization Of Lor And Sdh Enzymesmentioning

confidence: 99%

Lysine catabolism: flow, metabolic role and regulation

Fornazier

Braz. J. Plant Physiol.

Ferreira

et al. 2003

“…Lysine catabolism is controlled by the bifunctional protein LOR−SDH (EC 1.5.1.8 and EC 1.5.1.9, respectively) (). The LOR−SDH bifunctional enzyme has been purified and characterized in some plant species ( 12 , − and shown to be specific to the endosperm tissue in cereal crops ( , ). The studies involving mutants and transgenic plants provided a better understanding of lysine metabolism and indicated that in order to accumulate lysine in the seed, manipulation of its degradation is also needed ( 4 , 25 , 26 ).…”

Section: Introductionmentioning

confidence: 99%

Regulation of Lysine Metabolism and Endosperm Protein Synthesis by the Opaque-5 and Opaque-7 Maize Mutations

Lea

Damerval

et al. 2004

J. Agric. Food Chem.

Two high lysine maize endosperm mutations, opaque-5 (o5) and opaque-7 (o7), were biochemically characterized for endosperm protein synthesis and lysine metabolism in immature seeds. Albumins, globulins, and glutelins, which have a high content of lysine, were shown to be increased in the mutants, whereas zeins, which contain trace concentrations of lysine, were reduced in relation to the wild-type lines B77xB79+ and B37+. These alterations in the storage protein fraction distribution possibly explain the increased concentration of lysine in the two mutants. Using two-dimensional polyacrylamide gel electrophoresis of proteins of mature grains, variable amounts of zein polypeptides were detected and considerable differences were noted between the four lines studied. The analysis of the enzymes involved in lysine metabolism indicated that both mutants have reduced lysine catabolism when compared to their respective wild types, thus allowing more lysine to be available for storage protein synthesis.

“…The first two enzymatic steps are catalyzed by the bifunctional protein lysine 2-oxoglutarate reductase-saccharopine dehydrogenase (LOR-SDH; EC 1.5.1.8 and EC 1.5.1.9, respectively). LOR-SDH protein has been studied in some plant species [17][18][19][20][21] where the activity was particularly high in the endosperm tissue in cereal crops [17,18]. The regulation of the LOR activity has been shown to be complex, involving several distinct mechanisms [5,12,16].…”

mentioning

confidence: 99%

Regulation of maize lysine metabolism and endosperm protein synthesis by opaque and floury mutations

European Journal of Biochemistry

Damerval

Landry

et al. 2003

The capacity of two maize opaque endosperm mutants (o1 and o2) and two floury (fl1 and fl2) to accumulate lysine in the seed in relation to their wild type counterparts Oh43+ was examined. The highest total lysine content was 3.78% in the o2 mutant and the lowest 1.87% in fl1, as compared with the wild type (1.49%). For soluble lysine, o2 exhibited over a 700% increase, whilst for fl3 a 28% decrease was encountered, as compared with the wild type. In order to understand the mechanisms causing these large variations in both total and soluble lysine content, a quantitative and qualitative study of the N constituents of the endosperm has been carried out and data obtained for the total protein, nonprotein N, soluble amino acids, albumins/globulins, zeins and glutelins present in the seed of the mutants. Following two-dimensional PAGE separation, a total of 35 different forms of zein polypeptides were detected and considerable differences were noted between the five different lines. In addition, two enzymes of the aspartate biosynthetic pathway, aspartate kinase and homoserine dehydrogenase were analyzed with respect to feedback inhibition by lysine and threonine. The activities of the enzymes lysine 2-oxoglutate reductase and saccharopine dehydrogenase, both involved in lysine degradation in the maize endosperm were also determined and shown to be reduced several fold with the introduction of the o2, fl1 and fl2 mutations in the Oh43+ inbred line, whereas wild-type activity levels were verified in the Oh43o1 mutant.