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首页> 外文期刊>Journal of bacteriology >Characterization of Extradiol Dioxygenases from a Polychlorinated Biphenyl-Degrading Strain That Possess Higher Specificities for Chlorinated Metabolites
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Characterization of Extradiol Dioxygenases from a Polychlorinated Biphenyl-Degrading Strain That Possess Higher Specificities for Chlorinated Metabolites

机译：从多氯联苯降解菌株，对氯代代谢物具有更高特异性的二醇外加双加氧酶的表征。

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Recent studies demonstrated that 2,3-dihydroxybiphenyl 1,2-dioxygenase from Burkholderia sp. strain LB400 (DHBDLB400; EC 1.13.11.39) cleaves chlorinated 2,3-dihydroxybiphenyls (DHBs) less specifically than unchlorinated DHB and is competitively inhibited by 2′,6′-dichloro-2,3-dihydroxybiphenyl (2′,6′-diCl DHB). To determine whether these are general characteristics of DHBDs, we characterized DHBDP6-I and DHBDP6-III, two evolutionarily divergent isozymes from Rhodococcus globerulus strain P6, another good polychlorinated biphenyl (PCB) degrader. In contrast to DHBDLB400, both rhodococcal enzymes had higher specificities for some chlorinated DHBs in air-saturated buffer. Thus, DHBDP6-I cleaved the DHBs in the following order of specificity: 6-Cl DHB > 3′-Cl DHB ～ DHB ～ 4′-Cl DHB > 2′-Cl DHB > 4-Cl DHB > 5-Cl DHB. It also cleaved its preferred substrate, 6-Cl DHB, three times more specifically than DHB. Interestingly, some of the worst substrates for DHBDP6-I were among the best for DHBDP6-III (4-Cl DHB > 5-Cl DHB ～ 6-Cl DHB ～ 3′-Cl DHB > DHB > 2′-Cl DHB ～ 4′-Cl DHB; DHBDP6-III cleaved 4-Cl DHB two times more specifically than DHB). Generally, each of the monochlorinated DHBs inactivated the enzymes more rapidly than DHB. The exceptions were 4-Cl DHB for DHBDP6-I and 2′-Cl DHB for DHBDP6-III. As observed in DHBDLB400, chloro substituents influenced the reactivity of the dioxygenases with O2. For example, the apparent specificities of DHBDP6-I and DHBDP6-III for O2 in the presence of 2′-Cl DHB were lower than those in the presence of DHB by factors of >60 and 4, respectively. DHBDP6-I and DHBDP6-III shared the relative inability of DHBDLB400 to cleave 2′,6′-diCl DHB (apparent catalytic constants of 0.088 ± 0.004 and 0.069 ± 0.002 s?1, respectively). However, these isozymes had remarkably different apparent Km values for this compound (0.007 ± 0.001, 0.14 ± 0.01, and 3.9 ± 0.4 μM for DHBDLB400, DHBDP6-I, and DHBDP6-III, respectively). The markedly different reactivities of DHBDP6-I and DHBDP6-III with chlorinated DHBs undoubtedly contribute to the PCB-degrading activity of R. globerulus P6.
机译：最近的研究表明， Burkholderia sp。的2,3-二羟基联苯1,2-二加氧酶。菌株LB400（DHBD LB400 ; EC 1.13.11.39）比未氯化的DHB裂解的氯化2,3-二羟基联苯（DHBs）特异性更弱，并且被2'，6'-dichloro-2,3-竞争性抑制。二羟基联苯（2'，6'-diCl DHB）。为了确定这些是否是DHBDs的一般特征，我们对DHBD P6 -I和DHBD P6 -III进行了鉴定，这是 Rhodococcus globerulus 的两个进化差异同工酶。菌株P6，另一种优良的多氯联苯（PCB）降解剂。与DHBD LB400 相比，两种杜鹃球菌酶对空气饱和缓冲液中的某些氯化DHBs具有更高的特异性。因此，DHBD P6 -I按照以下特异性顺序切割DHB：6-Cl DHB> 3′-Cl DHB〜DHB〜4′-Cl DHB> 2′-Cl DHB> 4- Cl DHB> 5-Cl DHB。它还裂解了其优选的底物6-Cl DHB，特异性是DHB的三倍。有趣的是，DHBD P6 -I的最差底物是DHBD P6 -III的最佳底物（4-Cl DHB> 5-Cl DHB〜6-Cl DHB）。 〜3′-Cl DHB> DHB> 2′-Cl DHB〜4′-Cl DHB; DHBD P6 -III裂解4-Cl DHB的能力比DHB高两倍。通常，每个单氯化DHB比DHB更快地灭活酶。 DHBD P6 -I的4-Cl DHB和DHBD P6 -III的2'-Cl DHB除外。如在DHBD LB400 中观察到的，氯取代基影响双加氧酶与O 2 的反应性。例如，在2'-Cl DHB存在下，DHBD P6 -I和DHBD P6 -III对O 2 的表观特异性为分别比存在DHB的情况低60倍和4倍。 DHBD P6 -I和DHBD P6 -III具有DHBD LB400 不能裂解2'，6'-diCl DHB（表观催化）的相对能力。常数分别为0.088±0.004和0.069±0.002 s ？1 ）。但是，这些同工酶对该化合物的表观 K m 值有显着差异（DHBD LB400为0.007±0.001、0.14±0.01和3.9±0.4μM，DHBD P6 -I和DHBD P6 -III）。 DHBD P6 -I和DHBD P6 -III与氯化DHBs的明显不同的反应性无疑有助于 R的PCB降解活性。 P6。

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