ABSTRACT
L-theanine (γ-glutamylethylamide) is the main free amino acid component of tea and its favorable physiological effects on mammals have been reported. An enzymatic method for optically pure L-theanine production with a new L-aminoacylases-production fungi Cunnighamella echinulata 9980 was developed. The optimum conditions for enzymatic catalysis were at pH 6.5 with 50 mmol/L N-Acyl-DLtheanine and 40 mmol/L CoCl2. After 12-h incubation at 50℃,22.5 mmol/L L-theanine was obtained, the conversion rate against N-Acyl-L-theanine being 90%. Cunnighamella echinulata and the aminoacylase were applied in preparation of L-theanine.
ABSTRACT
L-theanine (γ-glutamylethylamide) is the main free amino acid component of tea and its favorable physiological effects on mammals have been reported. An enzymatic method for optically pure L-theanine production with a new L-aminoacylases-production fungi Cunnighamella echinulata 9980 was developed. The optimum conditions for enzymatic catalysis were at pH 6.5 with 50 mmol/L N-Acyl-DLtheanine and 40 mmol/L CoCl2. After 12-h incubation at 50℃,22.5 mmol/L L-theanine was obtained, the conversion rate against N-Acyl-L-theanine being 90%. Cunnighamella echinulata and the aminoacylase were applied in preparation of L-theanine.
ABSTRACT
Arginine Deiminase(ADI) was purified to homogeneity using ammonium sulfate precipitation,Q-Sepharose Fast Flow anion exchange chromatography and SephadexG-75 gel filtration chromatography. This purification protocol resulted in a 34.5-fold purification of ADI with 31.4% final yield. A molecular weight of about 190 kD determined by native gradient polyacrylamide gel electrophoresis. The enzyme has only one kind of 46 kD subunit determined by SDS-PAGE. Combining the results from the two kinds of electrophoresis,the authors deduce that the enzyme may be a tetramer. The optimum pH and temperature for lipolytic activity of ADI was pH 6.5 and 50℃,respectively. It was extremely stable at 45℃ and retained 97.9% of its original activity for 30 min. The stability declined rapidly as soon as the temperature rose over 50℃. ADI was highly stable in the pH range from pH 5-8. ADI acted on L-arginine but not on D-arginine. ADI catabolism was dependent on metal ions. At their adequate concentration,Mn2+,Mg2+ and Co2+ were the effective promoter,while superfluous Zn2+and Co2+ inhibited ADI activity. L-citrulline did not act on ADI,but L-ornithine inhibited ADI activity. The degradation of L-arginine with ADI catalysis was according to simple Michaelis-Menten equation. The Michaelis constant was 3.2686 mmol/L and the maxi-mum velocity was 2.44 ?mol/min.