Smith S B, Richards J W, Benisek W F
J Biol Chem. 1980 Apr 10;255(7):2678-84.
A delta 5-3-ketosteroid isomerase (EC 5.3.3.1) has been isolated from Pseudomonas putida Biotype B and purified to homogeneity. This previously undescribed steroid isomerase resembles that isolated from Pseudomonas testosteroni (Talalay, P., and Wang, V.S. (1955) Biochim. Biophys. Acta 18, 300-301). The enzyme is induced by various steroids, has a subunit molecular weight of 13,750 +/- 250, a pI of 4.8 +/- 0.1 has a specific activity of 40,000 units/mg, using 5-androstene-3,17-dione as the substrate. The amino acid composition of the enzyme subunit is Lys 2, His 2, Arg 8, Asp 11, Thr 5, Ser 4, Glu 17, Pro 8, Gly 12, Ala 12, Val 10, Met 5, Ile 6, Leu 8, Tyr 4, Phe 4, and Cys 4. The amino acid sequence has been determined for the NH2-terminal 50 residues. This portion of the polypeptide chain is approximately 47% homologous with the amino acid sequence of the first 50 residues of the delta 5-3-ketosteroid isomerase from P. testosteroni. The amino acid sequence of residues 33 to 41 of the P. putida isomerase is identical with the region Ala 31 through Pro 39 in the P. testosteroni enzyme. Residue 40 of the P. putida enzyme is aspartic acid and corresponds in the sequence to Asp 38 of the P. testosteroni isomerase, which has been shown to be essential for enzymatic activity (Ogez, J.R., Tivol, W.F., and Benisek, W.F. (1977) J. Biol. Chem. 252, 6151-6155).
已从恶臭假单胞菌生物型B中分离出一种δ5-3-酮甾体异构酶（EC 5.3.3.1）并纯化至同质。这种先前未描述的甾体异构酶类似于从睾丸酮假单胞菌中分离出的异构酶（塔拉莱，P.，和王，V.S.（1955年）《生物化学与生物物理学报》18，300 - 301）。该酶由多种甾体诱导产生，亚基分子量为13,750±250，pI为4.8±0.1，以5-雄烯-3,17-二酮为底物时比活性为40,000单位/毫克。酶亚基的氨基酸组成为：赖氨酸2个、组氨酸2个、精氨酸8个、天冬氨酸11个、苏氨酸5个、丝氨酸4个、谷氨酸17个、脯氨酸8个、甘氨酸12个、丙氨酸12个、缬氨酸10个、甲硫氨酸5个、异亮氨酸6个、亮氨酸8个、酪氨酸4个、苯丙氨酸4个和半胱氨酸4个。已测定了NH2末端50个残基的氨基酸序列。多肽链的这一部分与睾丸酮假单胞菌的δ5-3-酮甾体异构酶前50个残基的氨基酸序列约47%同源。恶臭假单胞菌异构酶33至41位残基的氨基酸序列与睾丸酮假单胞菌酶中31位丙氨酸至39位脯氨酸的区域相同。恶臭假单胞菌酶的40位残基是天冬氨酸，在序列中对应于睾丸酮假单胞菌异构酶的38位天冬氨酸，已证明该残基对酶活性至关重要（奥格兹，J.R.，蒂沃尔，W.F.，和贝尼塞克，W.F.（1977年）《生物化学杂志》252，6151 - 6155）。
