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Applied and Environmental Microbiology, September 1998, p. 3327-3331, Vol. 64, No. 9
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.

Purification and Characterization of L-Methionine gamma -Lyase from Brevibacterium linens BL2dagger

Benjamin Dias and Bart Weimer*

Western Dairy Center, Department of Nutrition and Food Sciences, Utah State University, Logan, Utah 84322-8700

Received 29 January 1998/Accepted 15 June 1998

L-Methionine gamma -lyase (EC 4.4.1.11) was purified to homogeneity from Brevibacterium linens BL2, a coryneform bacterium which has been used successfully as an adjunct bacterium to improve the flavor of Cheddar cheese. The enzyme catalyzes the alpha ,gamma elimination of methionine to produce methanethiol, alpha -ketobutyrate, and ammonia. It is a pyridoxal phosphate-dependent enzyme, with a native molecular mass of approximately 170 kDa, consisting of four identical subunits of 43 kDa each. The purified enzyme had optimum activity at pH 7.5 and was stable at pHs ranging from 6.0 to 8.0 for 24 h. The pure enzyme had its highest activity at 25°C but was active between 5 and 50°C. Activity was inhibited by carbonyl reagents, completely inactivated by DL-propargylglycine, and unaffected by metal-chelating agents. The pure enzyme had catalytic properties similar to those of L-methionine gamma -lyase from Pseudomonas putida. Its Km for the catalysis of methionine was 6.12 mM, and its maximum rate of catalysis was 7.0 µmol min-1 mg-1. The enzyme was active under salt and pH conditions found in ripening Cheddar cheese but susceptible to degradation by intracellular proteases.

* Corresponding author. Mailing address: Western Dairy Center, Department of Nutrition and Food Sciences, Utah State University, Logan, UT 84322-8700. Phone: (435) 797-3356. Fax: (435) 797-0103. E-mail: Milkbugs{at}cc.usu.edu.

dagger This is contribution 7006 from the Utah Agricultural Experiment Station.

Applied and Environmental Microbiology, September 1998, p. 3327-3331, Vol. 64, No. 9
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.


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