isolation and characterization of leucine dehydrogenase from a thermophilic citrobacter freundii jk-91strain isolated from jask port.

background and objectives: leucine dehydrogenase (leudh; ec 1.4.1.9) belongs to the amino acid dehydrogenase family and isused as a biocatalyst in medical and pharmaceutical industries (1). this study reported deals with the isolation and characterization of leudh from a thermophilic bacterium isolated from jask port in the province of hormozgan. materials and methods: aliquots of soil and water samples were cultured in leu specific medium and thermophilc bacteria that exhibited leudh activity were isolated and characterized biochemically. the leudh was purified and characterized in regard to the effects of ph and temperature on the activity, as well as its molecular weight determination. results: a thermophilic bacterium, citrobacter freundii strain jk-9 was identified and found to exhibit leudh activity. the enzyme characterization revealed that leudh exhibits higher activity at temperature range of 60 to 75°c (optimum of 60°c) and an optimum ph of activity at ph 10.5. the k value of leudh is 1.2 mm , while its molecular weight is about 320 kda, and consisted of eight subunits identical in molecular mass (40 kda). conclusion: briefly, a thermostableleudh enzyme from a strain of c. freundii was isolated and characterized. our data indicate that the c. freundii enzyme has potential for use in biotechnological applications.