Properties and secondary structure of tannase from Penicillium herquei

A tannase with a molecular mass of 72 kDa was obtained from Penicillium herquei isolated from valonia acorns following fermentation in a 5 L bioreactor. This tannase showed optimum activity at pH 6.0 and 30°C. The enzyme was inhibited by Fe 3+ , Zn 2+ , dithiothrietol (DTT), β-mercaptoethanol, formaldehyde, and ethanol, and induced by K + , Mn 2+ , Tween 80, and Triton X-100. The Michaelis constant ( K m ) and the second-order constant ( k cat / K m ) values of the tannase for propyl gallate (PG) were 0.62 mM and 174.1 mM/sec. The circular dichroism (CD) spectra indicated that the secondary structure of the tannase contained 14% α helix, 32.4% anti-parallel β-sheet, 4.8% β-sheet, 18.8% β-turn, and 30% random coil. Native tannase in ultrapure water manifested as spherical nano-particle aggregates with diameters ranging from 50 to 300 nm determined by atomic force microscopy (AFM).