Firestone M K, Tiedje J M
Appl Environ Microbiol. 1978 May;35(5):955-61. doi: 10.1128/aem.35.5.955-961.1978.
The pathway of degradation of nitrilotriacetate (NTA) was determined by using cell-free extracts and a 35-fold purification of NTA monooxygenase. The first step in the breakdown was an oxidative cleavage of the tertiary amine by the monooxygenase to form the aldo acid, glyoxylate, and the secondary amine, iminodiacetate (IDA). NTA N-oxide acted as a substrate analog for induction of the monooxygenase and was slowly metabolized by the enzyme, but was not an intermediate in the pathway. No intermediate before IDA was found, but an unstable alpha-hydroxy-NTA intermediate was postulated. IDA did undergo cleavage in the presence of the purified monooxygenase to give glyoxylate and glycine, but was not metabolized in cell-free extracts. Glyoxylate was further metabolized by cell-free extracts to yield CO2 and glycerate or glycine, products also found from NTA metabolism. Of the three bacterial isolates in which the NTA pathway has been studied, two strains, one isolated from a British soil and ours from a Michigan soil, appear to be almost identical.
通过使用无细胞提取物和对亚氨基三乙酸单加氧酶进行35倍纯化，确定了亚氨基三乙酸（NTA）的降解途径。分解的第一步是单加氧酶对叔胺进行氧化裂解，形成醛酸、乙醛酸和仲胺亚氨基二乙酸（IDA）。NTA N-氧化物作为单加氧酶诱导的底物类似物，被该酶缓慢代谢，但不是该途径的中间体。在IDA之前未发现中间体，但推测存在一种不稳定的α-羟基-NTA中间体。在纯化的单加氧酶存在下，IDA确实会裂解生成乙醛酸和甘氨酸，但在无细胞提取物中不被代谢。乙醛酸被无细胞提取物进一步代谢生成二氧化碳和甘油酸或甘氨酸，这些产物也可从NTA代谢中找到。在已研究NTA途径的三种细菌分离物中，有两种菌株，一种从英国土壤中分离，另一种是我们从密歇根土壤中分离的，似乎几乎相同。
