Association of inorganic-pyrophosphatase activity with human alkaline-phosphatase preparations

Abstract

1. The inorganic-pyrophosphatase activity of alkaline phosphatases prepared from human liver and small intestine was investigated at different stages of purification. 2. Both liver and intestinal preparations possessed pyrophosphatase activity at all stages of purification, and the two types of activity were not separated by gel filtration or by anion-exchange or cation-exchange chromatography. 3. After starch-gel electrophoresis of the tissue extracts, the zones of pyrophosphatase activity coincided exactly with alkaline-phosphatase zones. 4. Hydrolysis of each type of substrate was inhibited by the presence of the other, and a constant ratio of alkaline-phosphatase activity to pyrophosphatase activity was maintained during inactivation of the enzymes by incubation at 55 degrees . 5. These results are consistent with the view that alkaline phosphatases are also inorganic pyrophosphatases.

A New Enzymatic Method for Assaying Serum Inorganic Pyrophosphatase.

“…However, ALP from patients with hepatic diseases showed a relatively weak correlation with PPase activity (r=0,839), mainly due to a higher PPase to ALP ratio in the sera from patients with cirrhosis and hepatocellular carcinoma. A higher PPase to ALP ratio in intestine than in liver may influence the higher ratio in the sera from cirrhosis [2,3]. Furthermore, sera containing ALP originating from placenta showed a higher ratio of PPase activity to ALP activity compared with the other serum samples.…”

“…Thus, the ratio of PPase to ALP may vary according to the origin of ALP. Various reports have investigated the association of PPase with ALP by molecular size, net charge, thermal-inactivation studies, effects of various substances, and electrophoretic mobility after treatment with neuraminidase [1][2][3][4][5]. Many of these reports have supported the hypothesis that ALP and PPase are the same protein.…”

“…Various investigators have described methods for determining the activity and properties of PPase [1][2][3][4][5]. Shatton et al [6] reported on their method for * To whom correspondence should be addressed .…”

Tissue-nonspecific alkaline phosphatase and plasma cell membrane glycoprotein-1 are central antagonistic regulators of bone mineralization

“…It has been proposed that the activity of TNAP is required to generate the P i needed for hydroxyapatite crystallization (8-10), and ATP and PP i have been explored as potential substrates for this effect (11,28). However, the ability of TNAP to hydrolyze PP i also has been hypothesized to be important to promote calcification by hydrolyzing this potent inhibitor of mineralization (11-13, 29, 30).…”

“…TNAP is present in MVs (7), and it has been proposed that the inorganic phosphate (P i )-generating activity of TNAP is required to generate the P i needed for hydroxyapatite crystallization (8)(9)(10). However, the ability of TNAP to hydrolyze PP i also has been hypothesized to be important to promote osteoblastic mineralization (11,12), because PP i suppresses the formation and growth of hydroxyapatite crystals (13). In fact, heritable extracellular PP i deficiencies are models of ectopic calcification such as ankylosing spinal hyperostosis and pathologic soft-tissue ossification (14)(15)(16).…”