We report a catalytically promiscuous enzyme able to efficiently promote the hydrolysis of six different substrate classes. Originally assigned as a phosphonate monoester hydrolase (PMH) this enzyme exhibits substantial second-order rate accelerations ((
k
cat
/
K
M
)/
k
w
), ranging from 10
7
to as high as 10
19
, for the hydrolyses of phosphate mono-, di-, and triesters, phosphonate monoesters, sulfate monoesters, and sulfonate monoesters. This substrate collection encompasses a range of substrate charges between 0 and -2, transition states of a different nature, and involves attack at two different reaction centers (P and S). Intrinsic reactivities (half-lives) range from 200 days to 10
5
years under near neutrality. The substantial rate accelerations for a set of relatively difficult reactions suggest that efficient catalysis is not necessarily limited to efficient stabilization of just one transition state. The crystal structure of PMH identifies it as a member of the alkaline phosphatase superfamily. PMH encompasses four of the native activities previously observed in this superfamily and extends its repertoire by two further activities, one of which, sulfonate monoesterase, has not been observed previously for a natural enzyme. PMH is thus one of the most promiscuous hydrolases described to date. The functional links between superfamily activities can be presumed to have played a role in functional evolution by gene duplication.
我们报道了一种具有高度多能性的酶,能够有效促进六种不同底物类的水解。最初被归类为磷酰单酯水解酶(PMH)的这种酶,对于磷酸单酯、磷酸二酯、磷酸三酯、磷酰单酯、硫酸单酯和磺酸单酯的水解显示出显著的二级速率加速((
k
cat
/
K
M
)/
k
w
),范围从10
7
到高达10
19
。这一底物集合涵盖了在0到-2之间的底物电荷范围,具有不同性质的过渡态,并涉及两个不同的反应中心(P和S)。在近中性条件下的固有反应性(半衰期)从200天到10
5
年不等。对于一系列相对困难反应的显著速率加速表明,有效的催化不一定局限于仅仅一个过渡态的有效稳定。PMH的晶体结构将其归类为碱性磷酸酶超家族的一员。PMH包含了在这个超家族中以前观察到的四种原生活性,并通过另外两种活性扩展了其功能范围,其中之一,磺酸单酯酶,在天然酶中尚未观察到。因此,PMH是目前描述的最具多能性的水解酶之一。可以假设超家族活性之间的功能联系在通过基因复制进行功能进化中发挥了作用。