ABSTRACT A novel method for the determination of benzoic acid has been employed to identify carboxypeptidase activities in clinically relevant pathogens. Benzoic acid was determined after chemical derivatization by gas chromatography–mass spectrometry (GC–MS). N-Benzoyl amino acid substrates were evaluated for the detection of carboxypeptidase activities in a number of clinical pathogens. Upon enzymatic hydrolysis of these substrates, benzoic acid was produced which was detected by extraction from the liquid culture supernatant, derivatization as the trimethylsilyl ester, with subsequent analysis by GC–MS. Enzymatic hydrolysis of N-benzoyl glycine was observed for S. agalactiae, M. morganii, and A. baumannii. In addition, P. fluorescens was found to hydrolyze N-benzoyl-L-glutamic acid. Although the method provides an alternative approach for determining carboxypeptidase activity, ultimately it would not be a suitable method in a clinical setting. However, the method is well-suited for identifying carboxypeptidase activities that have not been previously described or to corroborate a carboxypeptidase assay with the ninhydrin reagent.

中文翻译：

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气相色谱-质谱法测定临床病原体中的羧肽酶活性

摘要 一种测定苯甲酸的新方法已被用于鉴定临床相关病原体中的羧肽酶活性。苯甲酸通过气相色谱-质谱 (GC-MS) 化学衍生化后测定。N-苯甲酰氨基酸底物用于检测许多临床病原体中的羧肽酶活性。在这些底物的酶促水解中，产生了苯甲酸，通过从液体培养上清液中提取，衍生为三甲基甲硅烷基酯，然后通过 GC-MS 进行分析来检测苯甲酸。观察到无乳链球菌、莫氏分枝杆菌和鲍曼不动杆菌的 N-苯甲酰甘氨酸的酶水解。此外，发现荧光假单胞菌水解 N-苯甲酰基-L-谷氨酸。尽管该方法提供了一种测定羧肽酶活性的替代方法，但最终它不是临床环境中的合适方法。然而，该方法非常适合用于鉴定以前未描述过的羧肽酶活性或用茚三酮试剂证实羧肽酶测定。