| Author(s) | Siham A. Al-Kadeeb and Dallal H. Al-Kalefa |
| Affiliation | Department of Botany, Girls College of Education in Riyadh P . O . Box 27104 , Riyadh 11417, Saudia Arabia |
| Title | L-alanine-glycine and L-alanine-glutamate- Transaminases of Rhizoctonia solani AG 4 |
| Source | Journal of King Saud University. Science. Volume 16, No 2. (2004/1424) |
| Abstract | Cell free extracts of Rhizoctonia solani AG 4 grown on L-alanine as the sole source of nitrogen were found to contain two L- alanine transaminases activities namely L-alanine- glycine and L-alanine-glutamate transaminase. The reversibility of L-alanine-glutamate transaminase catalyzed reaction was demonstrated. Alternatively, the transamination reaction catalyzed by L-alanine-glycine transaminase was found to be irreversible . The optimum activity of the first enzyme obtained at pH 8 and 40 oC , while that of the second enzyme obtained at pH 7.5 and 20 oC. Km values for all substrate was calculated. The activity of second enzyme was stimulated by addition of pyridoxal phosphate, whereas hydroxylamine inhibited it. The inhibitory effect of hydroxylamine was overcome by pyridoxal phosphate, while pyridoxal phosphate did not stimulate the activity of the first enzyme. Dialysis for 24 h against 0.05 M phosphate buffer at pH 8 completely inhibited the activity of the first enzyme, while the second enzyme was stable. From these result , it may be concluded that the two transamination reaction of L Ü alanine in R . solani AG 4 are catalyzed by two different transaminases . |
