Abstract
ALKALINE L-methioninase (E.C.4.4.1.11) from Aspergillus ustus AUMC 1051 was obtained in a good yield amounting to 1321 Unit(-1) (99.56 Ug(-1) bran) under solid state fermentation (SSF) of wheat bran. The enzyme was purified 15.83-fold with 62.63% yield after three steps of purification involved ammonium sulfate precipitation, Sephadex G-100 gel filtration and DEAE-cellulose ion exchange chromatography. The purified enzyme had a molecular mass of 46 kDa under denaturating conditions and an isoelectric point of 6. Maximal activity was recorded at pH 8.5 and 35 degrees C. Good stability of the purified enzyme was detected over wide pH values ranging from 8 to 10 and temperature up to 50 degrees C. The enzyme retained its full activity after 6 days of storage at 4 degrees C. Four weeks was found the T-1/2 of its activity. V-max and K-m, of the purified enzyme were found to be 820 Unit(-1) and 1.6 mM, respectively Alkaline L-methioninase activity was stimulated by Na and Co+2 and strongly inhibited by Hydroxylamine, iodoacetate, Hg+2 and Cu+2. The enzyme was proved to be glycoprotein containing -SH group in its catalytic site.