Shinozaki T, Pritzker K P
Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, ON, Canada.
J Rheumatol. 1996 Apr;23(4):677-83.
Alkaline phosphatase (ALP), an enzyme with pyrophosphatase (PPiase) activity can dissolve calcium pyrophosphate dihydrate (CPPD) crystals. We studied the effects of enzyme inhibitors such as bisphosphonates, orthovanadate, calcium, cadmium, and ascorbic acid on PPiase activity of ALP as well as on phosphate ester hydrolysis (Pase) activity and compared these effects to those on CPPD crystal dissolution.
An in vitro model system for crystal enzyme interaction was used to assess CPPD crystal dissolution.
Bisphosphonates inhibited ALP Pase activity more than ALP PPiase activity at the same concentrations. Calcium inhibited ALP PPiase activity, but not ALP Pase activity. Orthovanadate and cadmium inhibited ALP PPiase activity more than ALP Pase at the same concentrations. The inhibition rates of ALP PPiase at the same concentrations were orthovanadate > cadmium > calcium. Although ALP Pase activity was not inhibited, at high concentrations, ascorbic acid slightly inhibited ALP PPiase activity. Bisphosphonates at high concentrations inhibited ALP CPPD crystal dissolution. The strong inhibitory effects of bisphosphonates on ALP CPPD crystal dissolution compared to those on ALP PPiase activity suggest that bisphosphonates inhibit crystal dissolution by their affinity for the CPPD crystal surface. Calcium, orthovanadate, and cadmium inhibited ALP CPPD dissolution. The inhibition rates of ALP CPPD dissolution at the same concentrations were cadmium > calcium > orthovanadate. Ascorbic acid at high concentrations enhanced ALP CPPD dissolution.
These effects of different inhibitors on ALP PPiase and CPPD dissolution suggest that ALP CPPD crystal dissolution depends on binding of ALP CPPD crystals as well as the PPiase activity of the bound ALP. Because of its ubiquitous and broad phosphatase activity including PPiase activity, ALP may have a critical role in cell energy metabolism.
碱性磷酸酶（ALP）是一种具有焦磷酸酶（PPiase）活性的酶，能够溶解二水焦磷酸钙（CPPD）晶体。我们研究了双膦酸盐、原钒酸盐、钙、镉和抗坏血酸等酶抑制剂对ALP的PPiase活性以及磷酸酯水解（Pase）活性的影响，并将这些影响与对CPPD晶体溶解的影响进行比较。
使用晶体-酶相互作用的体外模型系统评估CPPD晶体溶解情况。
在相同浓度下，双膦酸盐对ALP的Pase活性的抑制作用比对ALP的PPiase活性的抑制作用更强。钙抑制ALP的PPiase活性，但不抑制ALP的Pase活性。在相同浓度下，原钒酸盐和镉对ALP的PPiase活性的抑制作用比对ALP的Pase活性的抑制作用更强。相同浓度下ALP的PPiase的抑制率为原钒酸盐>镉>钙。尽管ALP的Pase活性未受抑制，但在高浓度时，抗坏血酸会轻微抑制ALP的PPiase活性。高浓度的双膦酸盐抑制ALP对CPPD晶体的溶解。与对ALP的PPiase活性的抑制作用相比，双膦酸盐对ALP对CPPD晶体溶解的强烈抑制作用表明，双膦酸盐通过其对CPPD晶体表面的亲和力抑制晶体溶解。钙、原钒酸盐和镉抑制ALP对CPPD的溶解。相同浓度下ALP对CPPD溶解的抑制率为镉>钙>原钒酸盐。高浓度的抗坏血酸增强ALP对CPPD的溶解。
不同抑制剂对ALP的PPiase和CPPD溶解的这些影响表明，ALP对CPPD晶体的溶解取决于ALP与CPPD晶体的结合以及结合的ALP的PPiase活性。由于ALP具有包括PPiase活性在内的普遍存在且广泛的磷酸酶活性，它可能在细胞能量代谢中起关键作用。
