Interpretation and Clinical Significance of Alkaline Phosphatase Isoenzyme Patterns

Hoof, Viviane Van; Broe, Marc E. De

doi:10.3109/10408369409084677

Cited by 197 publications

(153 citation statements)

References 361 publications

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“…The substrate reports the biochemical activity of all AP isoforms (49), whereas levamisole sensitivity discriminates between NS AP, PLA AP, and I AP (50). The identity of the AP isoform(s) was further addressed with L-phenylalanine (I AP and PLA AP) and L-leucine (G AP) (34,35). All experiments were conducted as described above for enzyme assays.…”

Section: Methodsmentioning

confidence: 99%

“…Whereas ecto 5Ј-NT specifically dephosphorylates nucleoside monophosphates (AMP 3 adenosine (32)), APs will metabolize a spectrum of substrates, including 5Ј-nucleotides (ATP 3 ADP 3 AMP 3 adenosine), pyrophosphate, and p-nitrophenyl phosphate (33). The AP family contains four ectoenzymes: intestinal AP (I AP), tissue nonspecific AP detected in several organs including liver, bone, and kidney (NS AP), placental AP (PLA AP), and germ-cell AP (G AP) reported in testis and malignant tumors (34,35). Two AP isoforms have been localized in human airways: NS AP and PLA AP.…”

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confidence: 99%

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Ecto 5′-Nucleotidase and Nonspecific Alkaline Phosphatase

Picher

Burch

Hirsh

et al. 2003

Journal of Biological Chemistry

172

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In human airways, extracellular adenosine regulates epithelial functions supporting mucociliary clearance, an important airway defense mechanism against bacterial infection. Thus, defining the mechanisms of adenosine generation is critical for elucidating the role of this nucleoside in airway homeostasis. In this study, we identified the source of adenosine on the mucosal surface of human airway epithelia. Polarized primary cultures of human nasal or bronchial epithelial cells were assayed for transepithelial transport, cytosolic and cell surface adenosine production. Ussing chamber experiments indicated that serosal 1 M ). In bronchial cultures and tissues, ecto 5-NT accounted for >80% of total activity toward 0.01 mM AMP, compared with <15% for 5 mM AMP. The proximal airway AP isoform was identified as nonspecific AP (NS AP) by levamisole sensitivity and mRNA expression. The two ectoenzymes presented opposite airway distributions, ecto 5-NT and NS AP mRNA dominating in higher and lower airways, respectively. Collectively, these experiments support a major role for extracellular nucleotide catalysis and for ecto 5-NT and NS AP in the regulation of adenosine concentrations on airway surfaces. Mucociliary clearance (MCC)1 constitutes an essential component of airway defense against the development of infectious lung diseases (1). Several epithelial functions involved in MCC are regulated by extracellular nucleotides. For instance, P2Y 2 receptor activation by ATP or UTP-stimulated Ca 2ϩ -dependent Cl Ϫ channels (I CA ) (2, 3), cilia beating frequency (CBF) (4, 5), and mucin secretion from goblet cells and submucosal glands (6, 7). Two members of the P2X receptor subfamily were recently identified in human airway epithelial cultures: P2X 4 and P2X 5 (8). These ATP-gated cationic channels increased Ca 2ϩ -dependent Cl Ϫ secretion (8) and CBF (9) in airway epithelia. Interestingly, extracellular adenosine was found to be responsible for regulating the post-peak sustained phase of increased CBF induced by ATP on human nasal explants (4). In a human bronchial cell line lacking P2Y 2 receptors (Calu-3; Ref. 10), the channel activity of the cystic fibrosis transmembrane regulator was inhibited by 8-p-sulfophenyltheophylline, a nonspecific blocker of cell surface adenosine receptors (11). Subsequently, adenosine was shown to regulate CBF (4, 5) and ion transport (12-15) through activation of cell surface A 2B receptors.The importance of adenosine receptor-mediated regulation of MCC remains unclear because of the lack of information on endogenous sources of extracellular adenosine on the mucosal surface of airway epithelia. Adenosine could originate from the interstitial compartment and penetrate airway epithelial tight junctions to reach the lumen. The nucleoside could also be generated intracellularly by the cytosolic AMP-specific 5Ј-nucleotidase (CN-I) (16,17) and reach the mucosal surface through nucleoside transporters (for review see Ref. 18). Alternatively, ATP release and cell surface conversion into adenosine has...

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

Ecto 5′-Nucleotidase and Nonspecific Alkaline Phosphatase

Picher

Burch

Hirsh

et al. 2003

Journal of Biological Chemistry

172

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“…ALP is the most relevant enzyme in the diagnosis of bone diseases and is a commonly used marker for mature osteoblasts. 13) The elevation of ALP activity in lactoferrintreated osteoblasts implies that lactoferrin-enhanced ECM calcification would be dependent on ALP activation. We speculate that lactoferrin could adapt the immature osteoblasts into more differentiated phenotypes.…”

mentioning

confidence: 99%

Effect of Bovine Lactoferrin on Extracellular Matrix Calcification by Human Osteoblast-Like Cells

Takayama

Mizumachi

2008

Bioscience, Biotechnology, and Biochemistry

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“…ALP refers to a group of phosphomonoesterases that hydrolyze phosphate esters; most of the ALP in serum originates from either liver or bone, and higher serum-ALP concentrations occur in diseases affecting these organs. The bone-specific ALP is formed in osteoclasts and is thought to be involved in the calcification of the bone matrix, with elevated serum concentrations reflecting increased bone metabolism and accelerated bone formation (Van Hoof and De Broe 1994;Vroon and Israili 1990). Exclusion of subjects with liver disease or daily alcohol use did not materially change the difference in ALP between the two study groups, thus suggesting that changes in liver functions did not affect the results.…”

Section: Discussionmentioning

confidence: 99%