Developmental regulation of NAD+ kinase in Neurospora crassa

Abstract

The specific activity of NAD+ kinase (ATP:NAD+ 2'-phosphotransferase, EC 2.7.1.23) from Neurospora crassa shows sharp peaks when the organism enters a new developmental stage of the asexual life cycle: the peaks are observed during hydration and germination of conidia, at the transition from exponential to stationary growth and at the photostimulated conidiation. As stimulation of NAD+ kinase activity by light in conidiating mycelium is not sensitive to translation inhibitors, the activation of pre-existing molecules, rather than induction of protein synthesis de novo may be supposed. Enzyme electrophoresis revealed the presence of four forms of NAD+ kinase having different apparent molecular weights (I = 333,000; II = 306,000; III = 229,000 and IV = 203,000). Manifestation of the activity of individual forms of NAD+ kinase is developmentally controlled: form III is most abundant during vegetative growth, forms I and II prevail in conidia. At the conidial germination the increase of NAD+ kinase activity is associated with the activation of form III, whereas during photostimulation of conidiation form II is the most activated one. Therefore, certain molecular forms of the enzyme may be regarded as biochemical markers for different developmental stages of N. crassa.

Light regulation of metabolic pathways in fungi

“…NAD+ kinase is one of the key enzymes in regulation of relative levels of anabolic and catabolic pathways in the cell. In N. crassa , specific activity of NAD+ kinase increases only minutes after illumination up to twofold (Afanasieva et al 1982). This activation can be viewed as one step of a coordinated regulatory mechanism for the activity of enzymes involved in formation and reduction of NADP and consequently in regulation of the pentose phosphate shunt (Afanasieva et al 1982).…”

“…In N. crassa , specific activity of NAD+ kinase increases only minutes after illumination up to twofold (Afanasieva et al 1982). This activation can be viewed as one step of a coordinated regulatory mechanism for the activity of enzymes involved in formation and reduction of NADP and consequently in regulation of the pentose phosphate shunt (Afanasieva et al 1982). Moreover, both activities of NADH reductase and NADH oxidase (as well as several other enzymes involved in respiration) are negatively influenced by light not only in wild-type but also in albino strains (Ramadan-Talib and Prebble 1978) of N. crassa .…”

Neurospora crassaLight Signal Transduction Is Affected by ROS

“…For example, illumination increases the degree of phosphorylation of nucleoside diphosphate kinase [16], activates cAMP phosphodiesterase [41], and changes the activity of molecular forms of NAD + -kinase [42]. In addition, light changes the inactive (reduced) form of nitrate reductase into the active (oxidized) state [43].…”

Regulation of a NAD + Kinase Activity Isolated from Asynchronous Cultures of the Achlorophyllous ZC Mutant of Euglena gracilis

“…The N A D + kinase is therefore a key enzyme controlling the relative importance of anabolic and catabolic pathways in the cell. The total enzyme activity of N A D + kinase as well as the relative percentages of different molecular forms have already been shown to vary: in fungi (Afanasieva et al, 1982), in green plants (Allan and Trewavas, 1985) and in the silkworm in which the enzyme activity of different forms was ob served to be related to the regulation of ontogeny (Filippovich et al, 1990). Moreover, in plants, two types of N A D + kinase were shown to be either calm odulin-dependent or directly activated by Ca2+ (Marme, 1985;Roberts et al, 1985;Zhang eta l., 1994).…”