Chlorella enzyme activity

In our previous research, we found that the antialgal allelochemical Ethyl 2-Methylacetoacetate (EMA) caused loss of cell membrane integrity. It hinted that EMA may cause a change in the membrane. It is reported that environmental stress may increase the concentration of ROS in plant cell. The excessive ROS may cause a decrease of antioxidation enzymes activity and lipid peroxidation. The effect of EMA on the activity of SOD and POD and lipid fatty acids of Chlorella pyrenoidosa, Chlorella vulagaris and Microcystis aeruginosa were evaluated to elucidate the mode of action of EMA. 

Zeiler, K.G. Solomonson, L.P. (1989). Regulation of Chlorella nitrate reductase control of enzyme activity and immunoreactive protein levels by ammonia. Archives of Biochemistry and Biophysics 269, 46-54. 

Everest, S. A., Hipkin, C. R., and Syrett, P. J. (1986). Enzyme activities in some marine phytoplankters and the effect of nitrogen limitation on nitrogen and carbon metabolism in Chlorella stigmatophora. Mar. Biol. (Berl.) 90, 165-172. 

Accelerated detoxicating enzyme activity by Chlorella administration... 

Nucleotides have also been shown to inhibit glutamine synthetase from other sources, notably ADP, 5 -AMP, and CTP inhibit the enzyme from soybean root nodules (McParland et al., 1976), 5 -AMP and CTP that from E. coli (Woolfolk and Stadtman, 1967), B. subtilis (Deuel and Stadtman, 1970), and N. crassa (Kapoor and Bray, 1968), and 5 -AMP and CMP inhibit the Chlorella enzyme (Evstigneeva, et al., 1974). In contrast the rat liver and ovine brain enzymes are not appreciably inhibited by these nucleotides (Meister, 1974). When testing for inhibition by nucleotides it is necessary to have sufficient divalent cation present to ensure that inhibition is not simply a result of inadequate divalent cations due to chelation by the nucleotide. The variation in inhibition by nucleotides is dependent to some degree on the source of divalent metal cation thus O Neal and Joy (1975) found ADP and 5 -AMP to be more inhibitory to the Mg +-compared with the Mn +-dependent activity. 5 -AMP was also found to be more inhibitory to the magnesium dependent activity of B. subtilis enzyme (Deuel and Stadtman, 1970). 

With Fe(CN)j ". With a thiol as electron donor the enzyme from Chlorella is active with phosphoadenylyl-sulfate only in the presence of 3 -nucleotidase. 

From biochemical studies after in vitro isolation, NADH NR appears to be a soluble homodimeric enzyme (Pan Nason, 1978 Solomonson Barber, 1990), aggregating into tetramers at high concentration, as has been described in Chlorella and occasionally observed in higher plants. Both subunits (molecular mass 100-110 kDa) have recently been shown to be linked by a disulphide bond which can be reduced without loss of activity (Hyde et al., 1989). There is no direct evidence that a monomer subunit alone is active. Nevertheless, radiation inactivation analysis (Solomonson et al., 1987) provided a target size for Chlorella and spinach NADHrNR of 100 kDa, suggesting that indeed each subunit would behave independently as a functional NADH NR unit. 

In conclusion, it should be said that the PolyP-metabolizing enzymes in algae have been little studied. An activity, which transferred Pi from PolyP to ADP, was observed in cell-free extracts from Chlorella (Iwamura and Kuwashima, 1964) and Acetabularia (Rubtsov and Kulaev, 1977). Exopolyphosphatase activity was found in Acetabularia (Rubtsov and Kulaev, 1977), while polyphosphate glucokinase activity was not found in algae (Uryson and Kulaev, 1970). 

R. R. Schmidt (1966). Intracellular control of enzyme synthesis and activity during synchronous growth of Chlorella. In I. L. Cameron and G. M. Padilla (Eds), Cell Synchrony Studies in Biosynthetic Regulation, Academic Press, New York, pp. 189-198. 

GDH s of higher plants may bear some relationship to those isolated from Chlorella pyrenoidosa (51). A constitutive enz3rme, active with both NADH and NADPH, is separable by ion-exchange chromatography from an NADPH-specific enzyme that is induced by ammonia. However, glutamate synthase of higher plants may be the primary catalyst involved in glutamate formation (6 ). 

Morris, FI. J., Carrillo, O., Atinarales, Angel, Bermu dez, R. C., Lebeque, Y., Fontaine, R., Llaurado, G., and Beltra n, Y. (2007). tinmunostimulant activity of an enzymatic protein hydrolysate from green microalgae Chlorella vulgaris on undernourished mice. Enzyme Microb. Technol. 40, 456-460. 

Thiosulfonate reductase has been purified approximately 50-fold from Chlorella (Schmidt, 1973). In addition to catalyzing the reduction of the sulfonate moiety of GS-SOj by Fd d, it also catalyzes the reduction of dithionite to free sulfide using methylviologen. Schmidt (1973) found that the protein fraction which was labeled by GS- SOj in the absence of Fd,ed could be separated from thiosulfonate reductase and that the labeled protein in turn could be resolved into unlabeled protein and a labeled low molecular weight factor. When this factor was supplied to purified enzyme and activity measured by the dithionite/methylviologen assay, the activity was enhanced about threefold. No details of the kinetics of the presumed physiological reaction with bound sulfite and Fdrej are currently available. 

Vennesland s group has concluded that the inactivation in vivo after the cells have been treated with ammonia involves the formation of a firmly bound complex of reduced enzyme and cyanide. They have speculated that the product of ammonium assimilation which inhibits nitrate reductase is cyanide. In this respect the COj requirement for inactivation by ammonia in the light could be relevant. On the other hand, COg could potentiate the stimulating effect of ammonia on the photosynthetic non-cyclic electron flow.< If this interpretation would be correct, the activation of the ADP-dependent pyruvate kinase reaction by ammonia discovered by Bassham in Chlorella might be better explained by an increase in the cellular ADP level induced by the uncoupling effect of ammonia on photophosphorylation than by a direct activation of the kinase by the ammonium cation, as it has been postulated. 

The conversion in vitro of the active form of Chlorella nitrate reductase into the inactive form depends on its reduction by NAD(P)H, and is reversible by reoxidation with ferri-cyanide. Inactivation by NADH requires the first moiety of the complex to be active and proceeds much faster at high pH or when ADP at low concentration (0 3 mM) is simultaneously present. This synergistic effect is quite specific for NADH and ADP. Nitiate, as well as several of its competitive inhibitors, completely prevents and even reverses inactivation by NADH and ADP. In fact, Vennesland and co-workers have demonstrated the presence of cyanide in the in vivo inactivated enzyme by overnight incubation with nitrate and phosphate. ... 

---