Rinaldi A, Fadda M B, De Marco C
Physiol Chem Phys. 1978;10(1):47-57.
Snake venom L-aminoacid oxidase, while inactive on 4C and 5C dicarboxylic alpha-amino acids, may oxidize their 6C and 7C homologues alpha-aminoadipic and alpha-aminopimelic acid. It has been demonstrated that the enzyme also oxidizes S-carboxyethyl-L-cysteine and S-carboxymethyl-L-homocysteine, two analogues of alpha-aminopimelic acid with the gamma or delta methylene groups substituted by a sulfur atom. As oxidation products the corresponding ketoacids were obtained. Thus substrate specificity of L-aminoacid oxidase for dicarboxylic alpha-aminoacids seems highly dependent on the carbon chain length, whereas substitution of a methylene group by a sulfur atom seems to have almost no effect. On the other hand, D-aspartate oxidase from beef kidney (active on 4C to 6C dicarboxylic alpha-aminoacids) cannot oxidize the 7C alpha-aminopimelic acid but is active on the S-carboxyethyl-D-cysteine analogue. The other aminopimelic analogue, S-carboxymethyl-D-homocysteine, is a very poor substrate. Thus the substrate specificity of D-aspartate oxidase, highly dependent on chain length, is also influenced by chain conformation. Furthermore, oxidation of either compound under study, L-aminoacid oxidase and D-aspartate oxidase, leaves unaffected the thioether bond.
蛇毒L-氨基酸氧化酶虽然对4碳和5碳二羧酸α-氨基酸无活性，但可氧化其6碳和7碳同系物α-氨基己二酸和α-氨基庚二酸。已经证明该酶还可氧化S-羧乙基-L-半胱氨酸和S-羧甲基-L-高半胱氨酸，这两种α-氨基庚二酸的类似物中γ或δ亚甲基被硫原子取代。作为氧化产物，得到了相应的酮酸。因此，L-氨基酸氧化酶对二羧酸α-氨基酸的底物特异性似乎高度依赖于碳链长度，而亚甲基被硫原子取代似乎几乎没有影响。另一方面，来自牛肾的D-天冬氨酸氧化酶（对4碳至6碳二羧酸α-氨基酸有活性）不能氧化7碳α-氨基庚二酸，但对S-羧乙基-D-半胱氨酸类似物有活性。另一种氨基庚二酸类似物S-羧甲基-D-高半胱氨酸是一种非常差的底物。因此，高度依赖于链长的D-天冬氨酸氧化酶的底物特异性也受链构象的影响。此外，所研究的两种化合物L-氨基酸氧化酶和D-天冬氨酸氧化酶的氧化均不影响硫醚键。
