Lizcano J M, Escrich E, Ribalta T, Muntané J, Unzeta M
Departament de Bioquímica i Biologia Molecular, Facultat de Medicina, Universitat Autonama de Barcelona, Spain.
Biochem Pharmacol. 1991 Jul 5;42(2):263-9. doi: 10.1016/0006-2952(91)90712-e.
The activities and distribution of monoamine oxidase (MAO) and semicarbazide-sensitive amine oxidase (SSAO) in solid breast tumour induced in the rat by treatment with 7,12-dimethylbenz(alpha)anthracene (DMBA) were studied. The mammary tumours were classified according to anatomopathological criteria into: the benign fibroadenoma (FAD) and the malignant adenocarcinoma (ADC) and infiltrant adenocarcinoma (I-ADC). The proportions of total MAO (15%) and SSAO activities (85%) did not change with malignancy. However, an increasing degree of malignancy was associated with an increase in MAO-A activity and a decrease in MAO-B and SSAO activities. Kinetic constants were calculated for SSAO and for each MAO form separately, using specific substrates. The Km values did not change significantly with the degree of malignancy, but Vmax values for MAO-A increased whereas Vmax for SSAO and MAO-B diminished with malignancy. The dependence of SSAO activity on protein concentration indicated the presence of endogenous reversible inhibitory material in extracts from the more malign tumours. This inhibitor was associated with the microsomal fraction and was not removed by dialysis. It was also present in detergent-solubilized extracts, suggesting that the phenomenon might be due to an association of the enzyme itself producing an inactive species.
研究了用7,12-二甲基苯并(α)蒽（DMBA）处理诱导的大鼠实体乳腺肿瘤中单胺氧化酶（MAO）和氨基脲敏感胺氧化酶（SSAO）的活性及分布。根据解剖病理学标准将乳腺肿瘤分为：良性纤维腺瘤（FAD）、恶性腺癌（ADC）和浸润性腺癌（I-ADC）。总MAO活性（15%）和SSAO活性（85%）的比例不会随恶性程度而改变。然而，恶性程度的增加与MAO-A活性的增加以及MAO-B和SSAO活性的降低相关。使用特定底物分别计算了SSAO以及每种MAO形式的动力学常数。Km值不会随恶性程度而显著变化，但MAO-A的Vmax值增加，而SSAO和MAO-B的Vmax值随恶性程度降低。SSAO活性对蛋白质浓度的依赖性表明，在恶性程度更高的肿瘤提取物中存在内源性可逆抑制物质。这种抑制剂与微粒体部分相关，不能通过透析去除。它也存在于去污剂增溶的提取物中，这表明该现象可能是由于酶本身缔合产生无活性物质所致。
