ISSN:
1432-072X
Keywords:
Methanogenic bacteria
;
Archaebacteria
;
Methanopyrus
;
Hyperthermophiles
;
Thermostability
;
Tetrahydromethanopterin
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract The activity of purified N 5,N 10-methenyltetrahydromethanopterin cyclohydrolase from Methanopyrus kandleri was found to increase up to 200-fold when potassium phosphate was added in high concentrations (1.5 M) to the assay. A 200-fold stimulation was also observed with sodium phosphate (1 M) and sodium sulfate (1 M) whereas stimulation by potassium sulfate (0.8 M), ammonium sulfate (1.5 M), potassium chloride (2.5 M), and sodium chloride (2 M) was maximal 100-fold. A detailed kinetic analysis of the effect of potassium phosphate revealed that this salt exerted its stimulatory effect by decreasing the K m for N 5,N 10-methenyltetrahydromethanopterin from 2 mM to 40 μM and by increasing the V max from 2000 U/mg (kcat=1385 s-1) to 13300 U/mg (kcat=9200 s-1). Besides increasing the catalytic efficiency (kcat/K m) salts were found to protect the cyclohydrolase from heat inactivation. For maximal thermostability much lower concentrations (0.1 M) of salts were required than for maximal activity.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00245402
