Viggor Signe, Heinaru Eeva, Künnapas Allan, Heinaru Ain
Department of Genetics, Institute of Molecular and Cell Biology, University of Tartu, Riia 23, Tartu, Estonia.
Biodegradation. 2008 Sep;19(5):759-69. doi: 10.1007/s10532-008-9180-8. Epub 2008 Feb 19.
Phenol-degrading pseudomonads possessing different phenol hydroxylases (PH) were evaluated by the values of apparent half-saturation constant for phenol-oxygenating activity (K ( S )), maximum specific growth rate (mu (max)), lag-time length (lambda), inhibition constant (K ( I )) and growth yield factor (Y ( X/S )). Strains of the same PH type showed similar kinetic parameters: single-component PH (sPH) harbouring strains had higher values of K ( S ) and lower values of mu (max) than the strains having multicomponent PH (mPH). However, the values of K ( I ) and the dependencies of the lag-time length on initial phenol concentration were strain-specific. The elevated ratio between specific activities of catechol 1,2-dioxygenase (C12O) and muconate cycloisomerase in sPH-strains caused irreversible accumulation of a high amount of exogenous cis,cis-muconate (CCM) which resulted in decreased Y ( X/S ) values. Co-presence of sPH and mPH genes did not give the strains PC16 and P69 any extra advantage and according to determined kinetic parameters only one PH was active during phenol degradation. At the same time simultaneous functioning of catechol ortho and meta cleavage pathways (strain PC20) resulted in higher mu (max) and Y ( X/S ) values. Evaluation of strains showed that the type of PH determined the efficiency of phenol degradation, whereas the tolerance to elevated phenol concentrations was strain-specific.
通过苯酚氧化活性的表观半饱和常数（K(S)）、最大比生长速率（μ(max)）、延滞期长度（λ）、抑制常数（K(I)）和生长得率系数（Y(X/S)），对具有不同苯酚羟化酶（PH）的苯酚降解假单胞菌进行了评估。相同PH类型的菌株表现出相似的动力学参数：与具有多组分PH（mPH）的菌株相比，携带单组分PH（sPH）的菌株具有更高的K(S)值和更低的μ(max)值。然而，K(I)值以及延滞期长度对初始苯酚浓度的依赖性具有菌株特异性。sPH菌株中儿茶酚1,2 - 双加氧酶（C12O）和粘康酸环异构酶比活性之间的升高比例导致大量外源顺,顺 - 粘康酸（CCM）的不可逆积累，这导致Y(X/S)值降低。sPH和mPH基因的共同存在并没有赋予菌株PC16和P69任何额外优势，根据测定的动力学参数，在苯酚降解过程中只有一种PH具有活性。同时，儿茶酚邻位和间位裂解途径的同时运作（菌株PC20）导致更高的μ(max)和Y(X/S)值。对菌株的评估表明，PH类型决定了苯酚降解的效率，而对升高的苯酚浓度的耐受性具有菌株特异性。
