Paus E, Myklebust A T
Central Laboratory, Norwegian Radium Hospital, Oslo, Norway.
Tumour Biol. 1996;17(5):271-80. doi: 10.1159/000217989.
The isoforms of gamma-enolase were characterized in serum from patients with small-cell lung cancer (SCLC) and in extracts from SCLC cell lines and malignant melanoma tumor tissue. Large variations in the expression of the 3 gamma-isoforms of enolase were observed. These forms probably represent the homodimeric gamma gamma-enolase, the heterodimeric alpha gamma-enolase and the monomeric forms of gamma-enolase. Only the dimeric forms are enzymatically active. The predominant gamma-enolase in the cell lines is the heterodimeric alpha gamma-enolase. The SCLC cell lines can be divided into two groups: one with negligible gamma gamma-enolase expression and considerable amounts of the nonneuronal alpha alpha-enolase and a second group with a large fraction of gamma gamma-enolase concomitant with a low expression of alpha-enolase. Similar patterns are observed in tissue extracts from malignant melanoma. When changing buffer conditions by increasing the ionic strength and decreasing the Mg2+ concentration, interconversions between the isozymes occur. In contrast to the predominant alpha gamma-enolase in extracts from cell lines, the multiple forms of gamma-enolase in serum might be caused by a subunit exchange facilitated by the low Mg2+ concentration in plasma. However, there seems to be a stable equilibrium between the isoforms in undiluted patient serum. The induction of subunit exchange by perturbation in ionic strength and/or Mg2+ concentration indicates a need for caution when choosing diluents for use in assays for neuron-specific enolase.
在小细胞肺癌（SCLC）患者的血清、SCLC细胞系提取物以及恶性黑色素瘤肿瘤组织中对γ-烯醇化酶的同工型进行了表征。观察到烯醇化酶的3种γ-同工型的表达存在很大差异。这些形式可能代表同二聚体γγ-烯醇化酶、异二聚体αγ-烯醇化酶以及γ-烯醇化酶的单体形式。只有二聚体形式具有酶活性。细胞系中主要的γ-烯醇化酶是异二聚体αγ-烯醇化酶。SCLC细胞系可分为两组：一组γγ-烯醇化酶表达可忽略不计，非神经元αα-烯醇化酶含量可观；另一组大部分为γγ-烯醇化酶，同时α-烯醇化酶表达较低。在恶性黑色素瘤的组织提取物中也观察到类似模式。当通过增加离子强度和降低Mg2+浓度改变缓冲液条件时，同工酶之间会发生相互转化。与细胞系提取物中主要的αγ-烯醇化酶不同，血清中γ-烯醇化酶的多种形式可能是由血浆中低Mg2+浓度促进的亚基交换引起的。然而，在未稀释的患者血清中，同工型之间似乎存在稳定的平衡。离子强度和/或Mg2+浓度的扰动诱导亚基交换，这表明在选择用于神经元特异性烯醇化酶测定的稀释剂时需要谨慎。
