Malic enzyme has a dimer of dimers quaternary structure in which the dimer interface associates more tightly than the tetramer interface. In addition, the enzyme has distinct active sites within each subunit. The mitochondrial NAD(P)(+)-dependent malic enzyme (m-NAD(P)-ME) isoform behaves cooperatively and allosterically and exhibits a quaternary structure in dimer-tetramer equilibrium. The cyt...

In Drosophila melanogaster, the Sir2 gene and four Sir2-like genes have been found to be homologous to yeast SIR2 genes. To examine whether the fly Sir2, CG5216, and two Sir2-like genes, CG5085 and CG6284, affect life span, we suppressed their expression using RNAi. Decreased expression of the Sir2 and Sir2-like genes in all cells caused lethality during development. Suppression of the Sir2 in ...

Activation of Sir2-family proteins in response to calorie restriction (CR) has been proposed as an evolutionarily conserved mechanism for life span extension. This idea has been called into question with the discovery that Sir2-family proteins are not required for life span extension from CR in yeast. We present here a historical perspective and critical evaluation of the model that CR acts thr...

The C(4) photosynthetic pathway enriches carbon dioxide in the vicinity of Rubisco, thereby enabling plants to assimilate carbon more efficiently. Three canonical subtypes of C(4) exist, named after their main decarboxylating enzymes: NAD-dependent malic enzyme type, NADP-dependent malic enzyme type and phosphoenolpyruvate carboxykinase type. Cleome gynandra is known to perform NAD-ME type C(...

The histone deacetylase activity of Sir2p is dependent on NAD(+) and inhibited by nicotinamide (NAM). As a result, Sir2p-regulated processes in Saccharomyces cerevisiae such as silencing and replicative aging are susceptible to alterations in cellular NAD(+) and NAM levels. We have determined that high concentrations of NAM in the growth medium elevate the intracellular NAD(+) concentration thr...

Saccharomyces cerevisiae is calorie-restricted by lowering glucose from 2% to 0.5%. Under low glucose conditions, replicative lifespan is extended in a manner that depends on the NAD+-dependent protein lysine deacetylase Sir2 and NAD+ salvage enzymes. Because NAD+ is required for glucose utilization and Sir2 function, it was postulated that glucose levels alter the levels of NAD+ metabolites th...

Background: Phenylalanine dehydrogenase (PheDH EC 1.4.1.20) is a NAD+-dependent enzyme that performs the reversible oxidative deamination of L-phenylalanine to phenylpyruvate. It plays an important role in detection and screening of phenylketonuria (PKU) diseases and production of chiral intermediates as well. The main goal of this study was to find a simple and rapid alternative method for pur...

Ca(2+) ions play a critical role in the biochemical cascade of signal transduction pathways, leading to the activation of immune cells. In the present study, we show that the exposure of freshly isolated human monocytes to NAD(+) results in a rapid concentration-dependent elevation of [Ca(2+)](i) (intracellular free Ca(2+) concentration) caused by the influx of extracellular Ca(2+). NAD(+) deri...

We discovered that positively charged terbium complexes bearing 1,4,7,10-tetraazacyclododecane functionalized with amide ligands are highly sensitive to dynamic luminescence quenching by NAD(P)H. We exploited this phenomenon to establish a general time-resolved luminescence-based assay platform for sensitive detection of NAD(P)H-dependent enzyme activities.

Metabolic engineering studies have generally focused on manipulating enzyme levels through either the amplification, addition, or deletion of a particular pathway. However, with cofactor-dependent production systems, once the enzyme levels are no longer limiting, cofactor availability and the ratio of the reduced to oxidized form of the cofactor can become limiting. Under these situations, cofa...