Fitzsimmons Patrick N, Lien Gregory J, Nichols John W
U.S. Environmental Protection Agency, Office of Research and Development, National Health and Environmental Effects Research Laboratory, Mid-Continent Ecology Division, 6201 Congdon Boulevard, Duluth, Minnesota 55804, USA.
Comp Biochem Physiol C Toxicol Pharmacol. 2007 May;145(4):485-506. doi: 10.1016/j.cbpc.2006.12.011. Epub 2007 Jan 12.
Scientific literature from the past 25 years was searched to obtain in vitro biotransformation rate and affinity data for fish. To maximize the environmental relevance of this dataset, we focused on studies conducted at multiple substrate concentrations, and established acceptance criteria with respect to assay temperature and pH. Altogether, enzyme rate and affinity parameters are provided for 43 species and 77 compounds. In all but three instances, the reported reactions exhibited saturation at high substrate concentrations and could be used to calculate Michaelis-Menten rate (Vmax) and affinity (Km) constants. Most of this information was obtained using in vitro systems derived from liver tissue. Information from non-hepatic tissues was included, however, to provide a basis for comparisons among tissues. Where possible, in vitro enzyme parameters were examined to compare: (1) hepatic metabolism of a common substrate within a species, (2) hepatic metabolism of common substrates by different species, and (3) metabolism of a common substrate by different tissues of one species. Comparisons within species highlight a number of factors that may substantially influence xenobiotic metabolism in fish including gender, life stage, and acclimation temperature. Limited data suggest that Vmax and Km for the same reaction may vary by up to three orders of magnitude among species.
检索了过去25年的科学文献，以获取鱼类的体外生物转化速率和亲和力数据。为了使该数据集与环境的相关性最大化，我们重点关注了在多种底物浓度下进行的研究，并确定了关于测定温度和pH值的接受标准。总共提供了43种鱼类和77种化合物的酶速率和亲和力参数。除了三个实例外，所有报道的反应在高底物浓度下均表现出饱和，可用于计算米氏速率（Vmax）和亲和力（Km）常数。这些信息大多是使用源自肝脏组织的体外系统获得的。不过，也纳入了非肝脏组织的信息，以便为不同组织之间的比较提供依据。在可能的情况下，对体外酶参数进行了检查，以比较：（1）同一物种内一种常见底物的肝脏代谢，（2）不同物种对常见底物的肝脏代谢，以及（3）一个物种不同组织对一种常见底物的代谢。物种内的比较突出了一些可能对鱼类异生物质代谢产生重大影响的因素，包括性别、生命阶段和驯化温度。有限的数据表明，同一反应的Vmax和Km在不同物种之间可能相差多达三个数量级。
