Synthesis of nicontinamide-adenine dinucleotide by NAD pyrophosphorylase on a column of hydroxylapatite

Determination of NAD pyrophosphorylase activity in biological samples

A sensitive and simple method was developed for the accurate measurement of NAD pyrophosphorylase (NMN adenylyltransferase; EC 2.7.7.1) activity in biological samples. The reaction product of [4-3H]NAD was separated from the substrates [4-3H]NMN and ATP by HPLC. Under the standardized conditions of the assay, the enzyme activity in human chronic myelogenous leukemia K562 cells was found mainly in the nucleus (97%) with a sp act of 183.5 +/- 3.5 nmol/h/mg protein. The Km's for substrates NMN and ATP were 0.11 +/- 0.01 mM and 0.55 +/- 0.04 mM, respectively. This technique is highly reproducible with a 5% variation (SD) in five separate determinations. The lowest number of cells used for this enzyme assay was 41,000 with a protein content of 4 micrograms. The range of NAD produced during the assay was 2 to 200 microM. NAD pyrophosphorylase activities in the mononuclear cells of leukemic patients, human ovarian carcinoma cells, and rat liver were assayed.

Regeneration of nicotinamide cofactors for use in organic synthesis

The high cost of nicotinamide cofactors requires that they be regenerated in situ when used in preparative enzymatic synthesis. Numerous strategies have been tested for in situ regeneration of reduced and oxidized cofactors. Regeneration of reduced cofactors is relatively straightforward; regeneration of oxidized cofactors is more difficult. This review summarizes methods for preparation of the cofactors, factors influencing their stability and lifetime in solution, methods for their in situ regeneration, and process considerations relevant to their use in synthesis.

Purification and characterization of an inorganic pyrophosphatase from the extreme thermophile Thermus aquaticus

An inorganic pyrophosphatase was purified over 600-fold to homogeneity as judged by polyacrylamide gel electrophoresis. The enzyme is a tetramer of Mr = 84,000, has a sedimentation coefficient of 5.8S, a Stokes radius of 3.5 nm, and an isoelectric point of 5.7. Like the enzyme of Escherichia coli, the pyrophosphatase appears to be made constitutively. The pH and temperature optima are 8.3 and 80 degrees C, respectively. The Km for PPi is 0.6 mM. A divalent cation is essential, with Mg2+ preferred. The enzyme uses only PPi as a substrate.

The distribution of enzymes which synthesize nicotinamide adenine dinucleotide and nicotinamide adenine dinucleotide phosphate in monkey, rabbit, and ground squirrel retinas

The activity of adenosinetriphosphate:nicotinamide adenylyltransferase (EC 2.7.7.1) was measured in all the layers of monkey, rabbit, and ground squirrel retinas. Nicotinamide adenine dinucleotide (NAD) kinase (EC 2.7.1.23) distribution was measured in monkey and rabbit retinas. An attempt was made to measure NAD synthetase (EC 6.3.5.1), but the activities in the retinal layers were too low to produce a reliable increment in the levels of endogenous NAD. In monkey retina the adenylyl transferase was highest by far in the outer and inner nuclear layers, lower and variable in ganglion cell and fiber layers, and almost absent elsewhere. Rabbit retina differed in that activity was nearly absent in the outer nuclear layer, whereas in the ground squirrel outer nuclear layer activity was double that of the inner nuclear layer. The species differences suggest that adenylyl transferase is almost absent from cone cell nuclei and high in rod cell nuclei. NAD kinase distribution in monkey retina was almost the mirror image of that of adenylyl transferase.

The use of immobilized enzymes in the food industry: a review

The production of high fructose corn syrups was greatly facilitated by the use of immobilized glucose isomerase. Similarly, in Japan, the fermentation industry proved its processing efficiency for amino acids through the use of immobilized amino acid acylase. This article discusses the use of soluble enzymes in the food industry followed by a section on the various available methods to immobilize enzymes. Once enzymes are immobilized, many of their operational parameters could be altered. Rationale for the determination of the effects of immobilization is provided. A relatively new concept is the use of a single matrix for immobilizing more than one enzyme. Immobilized multi-enzyme systems offer many attractive advantages; however, such a process also raises some interesting questions about kinetics. These questions and their suggested answers are discussed in the penultimate section. The major emphasis of this article is on the use of immobilized enzymes in the food industry. Two systems--amino acylase and glucose isomerase--have been demonstrated to be techno-economically feasible. Immobilization of other enzymes, such as glucoamylase, lactase, protease, and flavor modifying enzymes, has received some attention. The potential of these new systems are also discussed.

Adenosine triphosphate: nicotinamide mononucleotide adenylyltransferase of pig liver. Purification and properties

Adenosine triphosphate : nicotinamide mononucleotide adenylyltransferase (EC 2.7.7.1) has been purifiec approximately 3500-fold from an extract of pig liver nuclei to a specific activity of 40 mumol of NAD+ per min per mg protein. The enzyme was found to have a molecular weight of 203 000, a frictional ratio of 1.6 and an isoelectric point of approximately 5. Michaelis constants for ATP and NMN were 0.11 mM and 0.12 mM, respectively.