Disease relevance of saccharopine

• To complete the studies on the enzymes associated with familial hyperlysinemia, saccharopine oxidoreductase was partially purified from human liver and characterized [1].
• Hyperlysinemia with saccharopinuria due to combined lysine-ketoglutarate reductase and saccharopine dehydrogenase deficiencies presenting as cystinuria [2].
• During attacks, these patients excreted alpha-keto-adipic, alpha-hydroxy-adipic, and alpha-aminoadipic acids, branched-chain keto acids and saccharopine in addition to lactic, pyruvic, and dicarboxylic acids characteristic of Reye syndrome [3].

High impact information on saccharopine

• We have isolated a cDNA clone, designated ZLKRSDH, encoding the bifunctional enzyme lysine-ketoglutarate reductase/saccharopine dehydrogenase (LKR/SDH) from maize [4].
• In yeast, lysine-ketoglutarate reductase and saccharopine dehydrogenase are encoded by the LYS1 and LYS9 genes, respectively, and we searched the available sequence databases for their human homologues [5].
• It is suggested that familial hyperlysinemia, type I, be applied to patients with major defects in lysine-ketoglutarate reductase and saccharopine dehydrogenase, and that familial hyperlysinemia, type II, to be used to designate patients in whom significant amounts of lysine-ketoglutarate reductase are retained [1].
• Chemical modification of the active site sulfhydryl group of saccharopine dehydrogenase (L-lysine-forming) [6].
• Both plants and animals catabolize lysine via saccharopine by two consecutive enzymes, lysine-ketoglutarate reductase (LKR) and saccharopine dehydrogenase (SDH), which are linked on a single polypeptide [7].

Biological context of saccharopine

• It catalyzes the reversible pyridine nucleotide-dependent oxidative deamination of saccharopine to generate alpha-Kg and lysine using NAD+ as an oxidizing agent [8].
• P. chrysogenum SR1- lacked saccharopine reductase activity, which was recovered after transformation of this mutant with the intact lys7 gene in an autonomously replicating plasmid [9].
• With the commercially available enzyme saccharopine dehydrogenase lysine formed either by decarboxylation of meso-diaminopimelate or by hydrolysis of L-alpha-amino-epsilon-caprolactam is converted to saccharopine with the concomitant oxidation of NADH, which is monitored by the decrease in absorbance at 340 nm [10].
• Saccharopine reductase is a homodimer, and each subunit consists of three domains, which are not consecutive in amino acid sequence [11].
• The two enzymes involved in lysine breakdown, lysine 2-oxoglutarate reductase (also known as lysine a-ketoglutarate reductase) and saccharopine dehydrogenase exist as a single bifunctional protein, with the former activity being regulated by lysine availability, calcium and phosphorylation/ dephosphorylation [12].

Anatomical context of saccharopine

• The generation of 14CO2 from [1-14C]lysine by hepatic mitochondria through the saccharopine pathway is controlled by intramitochondrial concentrations of lysine, 2-oxoglutarate and NADPH [13].
• Lysine-ketoglutarate reductase and saccharopine dehydrogenase activities were not detectable in extracts of cultured skin fibroblasts [2].

Associations of saccharopine with other chemical compounds

• Both in mammals and plants, excess lysine (Lys) is catabolized via saccharopine into alpha-amino adipic semialdehyde and glutamate by two consecutive enzymes, Lys-ketoglutarate reductase (LKR) and saccharopine dehydrogenase (SDH), which are linked on a single bifunctional polypeptide [14].
• The basic biochemical properties of the monofunctional SDH, including its pH optimum as well as the apparent Michaelis constant (K(m)) values for its substrates saccharopine and nicotinamide adenine dinucleotide at neutral and basic pH values, were similar to those of its SDH counterpart that is linked to LKR [15].
• Kinetic data have been measured for the histidine-tagged saccharopine dehydrogenase from Saccharomyces cerevisiae, suggesting the ordered addition of nicotinamide adenine dinucleotide (NAD) followed by saccharopine in the physiologic reaction direction [16].
• Inactivation of the lys7 gene, encoding saccharopine reductase in Penicillium chrysogenum, leads to accumulation of the secondary metabolite precursors piperideine-6-carboxylic acid and pipecolic acid from alpha-aminoadipic acid [9].
• Kinetic studies were consistent with an ordered sequence mechanism for LOR, where 2-oxoglutarate is the first substrate and saccharopine is the last product [17].

Gene context of saccharopine

• Five enzymes (homocitrate synthase, homoisocitrate dehydrogenase, alpha-aminoadipate aminotransferase, alpha-aminoadipate reductase and saccharopine dehydrogenase) were constitutively derepressed in all lys9 mutants with up to eight-fold higher enzyme levels than in isogenic wild-type cells [18].
• Thus, SPE3-LYS9 encodes functional spermidine synthase and saccharopine dehydrogenase gene products [19].
• Glutamate-alpha-ketoadipate transaminase, saccharopine reductase, and saccharopine dehydrogenase activities were demonstrated in extracts of Rhodotorula glutinis but alpha-aminoadipate reductase activity could not be measured in whole cells or in extracts [20].
• Crude and purified preparations of argininosuccinate synthetase, argininosuccinate lyase and arginase were subjected to inhibition studies with L-lysine and saccharopine [21].
• Mitochondria, isolated from rats pre-treated with glucagon, exhibited higher activities of L-lysine: 2-oxoglutarate reductase, saccharopine dehydrogenase and 2-aminoadipate aminotransferase [13].

Analytical, diagnostic and therapeutic context of saccharopine

• The molecular weight determinations by sedimentation equilibrium, Sephadex G-100 gel filtration, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis gave a value of about 39,000 and, therefore, saccharopine dehydrogenase is a single polypeptide chain enzyme [22].
• Cloning, expression, purification and crystallization of saccharopine reductase from Magnaporthe grisea [23].
• A reversed-phase, high performance liquid chromatography procedure was developed for the analysis of lysine, saccharopine, alpha-aminoadipic acid and pipecolic acid in mycelial extracts [24].

References