REGULATION OF THE "MALIC" ENZYME IN NEUROSPORA CRASSA

1967 ◽  
Vol 13 (9) ◽  
pp. 1211-1221 ◽  
Author(s):  
M. W. Zink
Keyword(s):  
Cell Growth ◽  
Neurospora Crassa ◽  
Growth Phase ◽  
Pyruvic Acid ◽  
Malic Acid ◽  
Malic Enzyme ◽  
Enzyme Preparation ◽  
Growth Cycle ◽  
Oxidative Decarboxylation ◽  
Enzyme Repression

"Malic" enzyme has been isolated from Neurospora crassa which can bring about the reversible carboxylation of pyruvic acid. The enzyme is specific to L-malate and NADP and is activated by Mn++ and Mg++. The partially purified enzyme does not decarboxylate oxaloacetate but is competitively inhibited by it. This enzyme is synthesized only during the early stages of the growth cycle and is repressed by acetate. In addition, the oxidative decarboxylation of malic acid is competitively inhibited by aspartic acid; the degree of inhibition depends upon the cell growth phase from which the enzyme is extracted. "Malic" enzyme isolated from a 12-h culture is not significantly inhibited by aspartate. However, this inhibition increases to 90% if an enzyme preparation from a 24-h culture is used. The significance of enzyme repression by acetate and the inhibition of the activity by aspartate are discussed.

scholarly journals Unidirectional inhibition and activation of ‘malic’ enzyme of Solanum tuberosum by meso-tartrate

1975 ◽  
Vol 149 (2) ◽  
pp. 349-355 ◽  
Author(s):  
K H Do Nascimento ◽  
D D Davies ◽  
K D Patil
Keyword(s):  
Solanum Tuberosum ◽  
Organic Acids ◽  
Malic Acid ◽  
Active Site ◽  
Malic Enzyme ◽  
Control Site ◽  
Oxidative Decarboxylation ◽  
Reductive Carboxylation ◽  
Similar Explanation ◽  
Stimulation Of

A kinetic study of ‘malic’ enzyme (EC 1.1.1.40) from potato suggests that the mechanism is Ordered Bi Ter with NADP+ binding before malate, and NADPH binding before pyruvate and HCO3-. The analysis is complicated by the non-linearity that occurs in some of the plots. meso-Tartrate is shown to inhibit the oxidative decarboxylation of malate but to activate the reductive carboxylation of pyruvate. To explain these unidirectional effects it is suggested that the control site of ‘malic’ enzyme binds organic acids (including meso-tartrate) which activate the enzyme. meso-Tartrate, however, competes with malate for the active site and thus inhibits the oxidative decarboxylation of malate. Because meso-tartrate does not compete effectively with pyruvate for enzyme-NADPH, its binding at the control site leads to a stimulation of the carboxylation of pyruvate. A similar explanation is advanced for the observation that malic acid stimulates its own synthesis.

Mechanism of regulation of the malic enzyme from Fusarium

1974 ◽  
Vol 20 (4) ◽  
pp. 443-454 ◽  
Author(s):  
M. W. Zink
Keyword(s):  
Malic Acid ◽  
Malic Enzyme ◽  
Kinetic Studies ◽  
Oxidative Decarboxylation ◽  
Mercaptosuccinic Acid ◽  
Substrate Activation ◽  
Phosphate Inhibition ◽  
Phosphoglyceric Acid ◽  
Variable Substrate ◽  
Text Component

The NADP-specific malic enzyme which catalyzes the oxidative decarboxylation of malic acid has been partially purified from extracts of Fusarium oxysporum and some of its kinetic parameters studied. Reciprocal velocity plots with malate as variable substrate are nonlinear except at high NADP concentration, while with NADP as variable substrate the reciprocal plots are linear. Substrate activation by malic acid describes a biphasic character in reciprocal plots. Kinetic studies indicate that there are two binding sites for malic acid. At saturating levels of NADP, two Km components for malic acid, designated as [Formula: see text] and [Formula: see text] are evident. The separation of the two components may have been accomplished; [Formula: see text] component by mercaptosuccinic acid and [Formula: see text] component by either low pH or by phosphate. Inhibition of the purified malic enzyme is nontotal with fructose 1,6-diphosphate, 6-phosphogluconic acid, and 3-phos-phoglyceric acid. The kinetic relationship between fructose 1,6-diphosphate or 6-phospho-gluconate and malic acid is competitive with respect to the [Formula: see text] component and noncompetitive with [Formula: see text] component. Inhibition by 3-phosphoglyceric acid and oxaloacetate with respect to both components is noncompetitive and competitive, respectively. The significance of negative cooperativity and the effect of the above-mentioned inhibitors is discussed.

scholarly journals Paenibacillus curdlanolyticus Strain B-6 Xylanolytic-Cellulolytic Enzyme System That Degrades Insoluble Polysaccharides

2006 ◽  
Vol 72 (4) ◽  
pp. 2483-2490 ◽  
Author(s):  
Patthra Pason ◽  
Khin Lay Kyu ◽  
Khanok Ratanakhanokchai
Keyword(s):  
Growth Phase ◽  
Enzyme Preparation ◽  
Enzyme System ◽  
Crude Enzyme ◽  
Cellulolytic Enzyme ◽  
Crude Enzyme Preparation ◽  
Multienzyme Complexes ◽  
Sds Page ◽  
Paenibacillus Curdlanolyticus ◽  
Cellulose Binding

ABSTRACT A facultatively anaerobic bacterium, Paenibacillus curdlanolyticus B-6, isolated from an anaerobic digester produces an extracellular xylanolytic-cellulolytic enzyme system containing xylanase, β-xylosidase, arabinofuranosidase, acetyl esterase, mannanase, carboxymethyl cellulase (CMCase), avicelase, cellobiohydrolase, β-glucosidase, amylase, and chitinase when grown on xylan under aerobic conditions. During growth on xylan, the bacterial cells were found to adhere to xylan from the early exponential growth phase to the late stationary growth phase. Scanning electron microscopic analysis revealed the adhesion of cells to xylan. The crude enzyme preparation was found to be capable of binding to insoluble xylan and Avicel. The xylanolytic-cellulolytic enzyme system efficiently hydrolyzed insoluble xylan, Avicel, and corn hulls to soluble sugars that were exclusively xylose and glucose. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of a crude enzyme preparation exhibited at least 17 proteins, and zymograms revealed multiple xylanases and cellulases containing 12 xylanases and 9 CMCases. The cellulose-binding proteins, which are mainly in a multienzyme complex, were isolated from the crude enzyme preparation by affinity purification on cellulose. This showed nine proteins by SDS-PAGE and eight xylanases and six CMCases on zymograms. Sephacryl S-300 gel filtration showed that the cellulose-binding proteins consisted of two multienzyme complexes with molecular masses of 1,450 and 400 kDa. The results indicated that the xylanolytic-cellulolytic enzyme system of this bacterium exists as multienzyme complexes.

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