Abstract：
Heme proteins perform a variety of biological functions and also play significant roles in the field of bio-catalysis. The β-lactamase activity of heme proteins has rarely been reported. Herein, we found, for the first time, that myoglobin (Mb), an O2 carrier, also exhibits novel β-lactamase activity by catalyzing the hydrolysis of ampicillin. The catalytic proficiency ((kcat/KM)/kuncat) was determined to be 6.25 × 1010, which is much higher than the proficiency reported for designed metalloenzymes, although it is lower than that of natural β-lactamases. Moreover, we found that this activity could be regulated by an engineered disulfide bond, such as Cys46-Cys61 in F46C/L61C Mb or by the addition of imidazole to directly coordinate to the heme center. These results indicate that the heme active site is responsible for the β-lactamase activity of Mb. Therefore, the study suggests the potential of heme proteins acting as β-lactamases, which broadens the diversity of their catalytic functions.
摘要：
血红素蛋白具有多种生物学功能，在生物催化领域也发挥着重要作用。血红素蛋白的β-内酰胺酶活性鲜有报道。在这里，我们发现,第一次,肌红蛋白（Mb），O2载体，还通过催化氨苄青霉素的水解表现出新的β-内酰胺酶活性。催化能力（（kcat/KM）/kuncat）被确定为6.25×1010，远高于针对设计的金属酶报告的能力，尽管它低于天然β-内酰胺酶。此外，我们发现这种活性可以通过工程改造的二硫键来调节，例如Cys46-Cys61在F46C/L61CMb中或通过添加咪唑直接与血红素中心配位。这些结果表明血红素活性位点负责Mb的β-内酰胺酶活性。因此,这项研究表明血红素蛋白作为β-内酰胺酶的潜力，这扩大了它们催化功能的多样性。
