Paulus T J, Switzer R L
J Bacteriol. 1979 Jan;137(1):82-91. doi: 10.1128/jb.137.1.82-91.1979.
The number and properties of carbamyl phosphate synthetases in Bacillus subtilis have been uncertain because of conflicting genetic results and instability of the enzyme in extracts. The discovery of a previously unrecognized requirement of B. subtilis carbamyl phosphate synthetases for a high concentration of potassium ions for activity and stability permitted unequivocal demonstration that this bacterium elaborates two carbamyl phosphate synthetases. Carbamyl phosphate synthetase A was shown to be repressed by arginine, to have a molecular weight of about 200,000, and to be coded for by a gene that maps near argC4. This isozyme was insensitive to metabolites of the arginine and pyrimidine biosynthetic pathways. Carbamyl phosphate synthetase P was found to be repressed by uracil, to have a molecular weight of 90,000 to 100,000, and to be coded for by a gene that maps near the other pyr genes. This isozyme was activated by phosphoridine nucleotides. Other kinetic properties of the two isozymes were compared. Bacillus thus resembles eucaryotic microbes in producing two carbamyl phosphate synthetases, rather than the enteric bacteria, which produce a single carbamyl phosphate synthetase.
由于遗传结果相互矛盾以及该酶在提取物中的不稳定性，枯草芽孢杆菌中氨甲酰磷酸合成酶的数量和性质一直不明确。发现枯草芽孢杆菌氨甲酰磷酸合成酶之前未被认识到的对高浓度钾离子的活性和稳定性需求，使得能够明确证明这种细菌产生两种氨甲酰磷酸合成酶。氨甲酰磷酸合成酶A被证明受精氨酸抑制，分子量约为200,000，由位于argC4附近的一个基因编码。这种同工酶对精氨酸和嘧啶生物合成途径的代谢产物不敏感。氨甲酰磷酸合成酶P被发现受尿嘧啶抑制，分子量为90,000至100,000，由位于其他嘧啶基因附近的一个基因编码。这种同工酶被磷酸化核苷激活。比较了这两种同工酶的其他动力学性质。因此，枯草芽孢杆菌在产生两种氨甲酰磷酸合成酶方面类似于真核微生物，而不像产生单一氨甲酰磷酸合成酶的肠道细菌。
