Hu S, Treat R W, Kincaid J R
Chemistry Department, Marquette University, Milwaukee, Wisconsin 53233.
Biochemistry. 1993 Sep 28;32(38):10125-30. doi: 10.1021/bi00089a031.
Low-frequency resonance Raman spectra of the cyanide and carbon monoxide adducts of lactoperoxidase are obtained with Soret excitation. The nu(Fe-CN) and delta(Fe-C-N) modes are detected at 360 and 453 cm-1, respectively. Upon the isotopic substitution of 13C14N, 12C15N, and 13C15N, the band at 453 cm-1 in the natural abundance adduct shifts to 448, 452, and 445 cm-1, while the 360-cm-1 peak shifts to 358, 357, and 356 cm-1, respectively. The 360-cm-1 band is shifted to 355 cm-1 when the pH is changed from 7.0 to 10.5. On the basis of a previous normal-mode analysis of the cyanoferric adduct of myeloperoxidase, a bent Fe-C-N linkage is suggested for the cyanide adduct of lactoperoxidase. The nu(Fe-CN) (374 cm-1) and delta(Fe-C-N) (480 cm-1) modes are observed for the cyanide adduct of reduced lactoperoxidase. For the carbon monoxide adduct, the nu(Fe-CO) (533 cm-1) and delta(Fe-C-O) (578 cm-1) modes at pH 7.0 are observed to shift to 498 and 570 cm-1 as the pH is raised from 7.0 to 10.0. The strong intensity of delta(Fe-C-O) at both acid and alkaline pHs, along with a suggested bent structure of the Fe-C-N moiety, implies a narrow heme pocket for lactoperoxidase.
用索雷特激发获得了乳过氧化物酶的氰化物和一氧化碳加合物的低频共振拉曼光谱。分别在360和453 cm-1处检测到ν(Fe-CN)和δ(Fe-C-N)模式。在13C14N、12C15N和13C15N进行同位素取代后，天然丰度加合物中453 cm-1处的谱带分别移至448、452和445 cm-1，而360 cm-1处的峰分别移至358、357和356 cm-1。当pH从7.0变为10.5时，360 cm-1处的谱带移至355 cm-1。基于先前对髓过氧化物酶的氰基铁加合物的正常模式分析，推测乳过氧化物酶的氰化物加合物存在弯曲的Fe-C-N键。在还原型乳过氧化物酶的氰化物加合物中观察到ν(Fe-CN)（374 cm-1）和δ(Fe-C-N)（480 cm-1）模式。对于一氧化碳加合物，当pH从7.0升高到10.0时，在pH 7.0处观察到的ν(Fe-CO)（533 cm-1）和δ(Fe-C-O)（578 cm-1）模式分别移至498和570 cm-1。在酸性和碱性pH条件下，δ(Fe-C-O)的强度都很强，同时Fe-C-N部分存在弯曲结构，这意味着乳过氧化物酶的血红素口袋较窄。
