Properties of alkaline phosphatase in the gingival crevicular fluid

The isoenzymic properties of the alkaline phosphatase (ALP) of the gingival crevicular fluid (GCF) were investigated and compared with those in other cells, such as human polymorphonuclear leukocytes (PMNs), and human periodontal ligament cells (PDLs), and with those of three species of periodontopathic bacteria: Porphyromonas gingivalis 381 (P. gingivalis), Prevotella intermedia ATCC25611 (P. intermedia), and Capnocytophaga sputigena ATCC33123 (C. sputigena). The biochemical properties of the isoenzymes were analyzed by the following methods: enzyme assays, inhibition pattern using three chemical inhibitors, 4 to 20% gradient polyacrylamide gel electrophoresis, thermostability, immunological specificity, and phosphatidylinositol-specific phospholipase C (PI-PLC) treatment. The inhibition experiment showed that ALP of the PMNs and PDLs possessed almost the same enzymatic properties of tissue-nonspecific ALP (bone/liver/kidney; TNSALP), and the ALP of the three species of periodontopathic bacteria possessed specific properties that were different from those of TNSALP, intestinal, or placental ALP. The ALP of the GCF was only slightly susceptible to levamisole (1 mM), L-phenylalanine (20 mM), and SDS (1%). An electrophoresis thermostability test demonstrated that the enzyme activity of the GCF was separated into one or two bands. The main heat-labile slow band contained the phosphatidylinositol (PI)-moiety-anchored ALP and possessed immunological specificity against anti-bone type ALP. The minor fast band was heat stable and showed mobility similar to that in P. gingivalis. These results indicated that the ALP of the GCF consisted of several ALP isoenzyme types whose possible origins are considered to be derived from phosphatidylinositol (PI) anchored ALP and periodontopathic bacterial ALP.