In the presence of CoA, cell-free extracts prepared from porcine liver was found to convert 7,8-dihydroxyflavone (DHF) to a pantetheine conjugate, which was a novel flavonoid. We purified a 7,8-DHF-converting enzyme from the extracts, and identified it as hemoglobin (Hb). The purified Hb showed the following two activities: (i) degradation of CoA into pantetheine through hydrolytic cleavage to yield pantetheine and 3'-phospho-adenosine-5'-diphosphate (ADP) independently of heme, and (ii) addition of a thiol (e.g., pantetheine, glutathione and cysteine) to 7,8-DHF through C-S bond formation. Human Hb also exhibited the above flavonoid-converting activity. In addition, heme-containing enzymes such as peroxidase and catalase added each of pantetheine, glutathione and cysteine to the flavonoid, although no pantetheine conjugates were synthesized when CoA was used as a substrate. These findings indicated that the thiol-conjugating activity is widely observed in heme-containing proteins. On the other hand, only Hb catalyzed the hydrolysis of CoA, followed by the thiol conjugation to synthesize the pantetheine conjugate. To the best of our knowledge, this is the first report showing that Hb has the catalytic ability to convert naturally occurring bioactive compounds, such as dietary flavonoids, to the corresponding conjugates in the presence of thiol donors or CoA.

中文翻译：

---

血红蛋白催化CoA降解和向类黄酮中添加硫醇。

在CoA的存在下，发现从猪肝中提取的无细胞提取物可将7,8-二羟基黄酮（DHF）转化为泛肽缀合物，后者是一种新型的类黄酮。我们从提取物中纯化了7,8-DHF转化酶，并将其鉴定为血红蛋白（Hb）。纯化的血红蛋白具有以下两个活性：（i）通过水解裂解将CoA降解为泛胺，生成泛素和3'-磷酸-腺苷-5'-二磷酸酯（ADP），与血红素无关，以及（ii）添加硫醇（例如泛酸，谷胱甘肽和半胱氨酸）通过CS键形成7,8-DHF。人血红蛋白也表现出上述的类黄酮转化活性。此外，含血红素的酶（例如过氧化物酶和过氧化氢酶）将泛酸，谷胱甘肽和半胱氨酸分别添加到类黄酮中，虽然当使用CoA作为底物时没有合成泛肽结合物。这些发现表明，在含血红素的蛋白质中广泛观察到了硫醇结合活性。另一方面，只有Hb催化CoA的水解，然后进行巯基结合以合成泛肽结合物。据我们所知，这是第一个报道，表明Hb具有催化能力，可在硫醇供体或CoA存在下将天然存在的生物活性化合物（如膳食类黄酮）转化为相应的结合物。