The lipase was partially purified by ion exchange chromatography and gel filtration column chromatography, and was characterized from Geobacillus stearothermophilus AH22 strain. The lipase was purified 18.3-folds with 19.7% recovery. The lipase activity was determined by using p-nitrophenyl esters (C2-C12) as substrates. The Km values of the enzyme for these substrates were found as 0.16, 0.02, 0.19 and 0.55 mM, respectively, while Vmax values were 0.52, 1.03, 0.72 and 0.15 U mg(-1). The enzyme showed maximum activity at 50 °C and between pH 8.0 and 9.0. The enzyme was found to be quite stable at pH range of 4.0-10.0, and thermal stability between 50 and 60 °C. It was found that the best inhibitory effect of the enzyme activity was of Hg(2+). The inhibitory effect as orlistat, catechin, propyl paraben, p-coumaric acid, 3,4-dihydroxy hydro-cinnamic acid was examined. These results suggest that G. stearothermophilus AH22 lipase presents very suitable properties for industrial applications.

ABSTRACT

An α-carbonic anhydrase (CA, EC 4.2.1.1) was purified and characterized kinetically from gill of Acipenser gueldenstaedtii as an endangered sturgeon species. The carbonic anhydrase was purified 66-folds with yield 20.7% by Sepharose-4B-l-tyrosine-sulfanilamide affinity column and the specific activity was determined as 222.2 EU/mg protein. Km and Vmax kinetic values for gill carbonic anhydrase were calculated by a Lineweaver-Burk graph using p-nitrophenol acetate (p-NPA) as a substrate, and was defined as 2.5 mM and 5 × 10(6 )μM/min, respectively. It was observed that CA from the sturgeon gill in the presence of the sulfanilamide and acetazolamide as an inhibitor had very low IC50 values such as 13.0 and 0.1 μM, respectively. In addition, it was determined that the enzyme was inhibited by Fe(2+,) Co(2+,) Ni(2+), and Zn(2+)-Ba(2+) with the IC50 values of 0.2, 1.7, 1.2, and 1.1 mM, respectively.

The electronic structure of binary compounds AlN and GaN are presented. We have used the empirical pseudo-potential method. Good agreement between the calculated results and experiment is obtained. The charge densities are presented for the sum of the four valence bands of both AlN and GaN.