Lessie T G, Whiteley H R
J Bacteriol. 1969 Nov;100(2):878-89. doi: 10.1128/jb.100.2.878-889.1969.
A threonine deaminase susceptible to inhibition by isoleucine was purified over 3,000-fold from extracts of Pseudomonas multivorans, a bacterium able to use threonine or alpha-ketobutyrate as sole source of carbon and energy. The enzyme was characterized with respect to molecular weight, dissociation to subunits, and apparent affinities for threonine, isoleucine, and several other ligands. Certain features of the enzyme including its reversible dissociation to subunits, its high constitutive activity, its marked stability, and high apparent orders of binding for threonine and isoleucine were unusual compared to those of isoleucine-inhibitable enzymes from other bacteria. These findings suggested some relationship between properties of the enzyme and the ability of P. multivorans to use threonine as sole carbon source. However, mutant studies ruled out a direct role of the enzyme in threonine catabolism and indicated that another enzyme, threonine dehydrogenase, is essential for growth on threonine.
从多食假单胞菌提取物中纯化出一种对异亮氨酸抑制敏感的苏氨酸脱氨酶，纯化倍数超过3000倍。多食假单胞菌是一种能够利用苏氨酸或α-酮丁酸作为唯一碳源和能源的细菌。对该酶的分子量、亚基解离以及对苏氨酸、异亮氨酸和其他几种配体的表观亲和力进行了表征。与来自其他细菌的异亮氨酸抑制性酶相比，该酶的某些特性，包括其可逆解离为亚基、高组成活性、显著稳定性以及对苏氨酸和异亮氨酸的高表观结合级数，都不寻常。这些发现表明该酶的特性与多食假单胞菌利用苏氨酸作为唯一碳源的能力之间存在某种关系。然而，突变体研究排除了该酶在苏氨酸分解代谢中的直接作用，并表明另一种酶，即苏氨酸脱氢酶，对于在苏氨酸上生长至关重要。
