The two isozymes of rat intestinal alkaline phosphatase are products of two distinct genes

Abstract

Rat intestinal alkaline phosphatases (IAP-I and -II) differ in primary structure, substrate specificity, tissue localization, and response to fat feeding. This study identifies two distinct genes ( approximately 5-6 kb) corresponding to each isozyme and containing 11 exons of nearly identical size. The exon-intron junctions are identical with those found in IAP genes from other species. The 1.7 and 1.2 bp of 5' flanking regions isolated from each gene, respectively, contain Sp1 and gut-enriched Kruppel-like factor (GKLF) binding sites, but otherwise show little identity. There is a potential CAAT-box 14 bp 5' to the transcriptional start site, 36 bp upstream from IAP-I, and a TATA-box 31 bp 5' to the transcriptional start site, 55 bp upstream from IAP-II. Transfection of these promoter regions (linked to luciferase as a reporter gene) into a kidney cell line, COS-7, produced the differential response to oleic acid expected from in vivo studies, i.e., threefold increase using the 5' flanking region of IAP-II, but not IAP-I. This response was not reproduced by 5,8,11,14-eicosatetraynoic acid (ETYA) or clofibrate, suggesting that peroxisome proliferator response elements are not involved. Isolation of the IAP-II gene will allow determination of the sequences responsible for dietary fat response in the enterocyte.

Characterization of rat heart alkaline phosphatase isoenzymes and modulation of activity

“…After an acute fat feeding, Int-ALP type II expression is increased in liver (where Int-ALP type I is not expressed) and Int-ALP type II expression increases five times more than Int-ALP type I in the duodenum (4,21,22). It is interesting to note that rat liver and heart, tissues that can use fat as an energy source in several physiological states, express the same Int-ALP gene.…”

Decreased sucrase and lactase activity in iron deficiency is accompanied by reduced gene expression and upregulation of the transcriptional repressor PDX-1

“…This decreased activity cannot be attributable to changes in kinetic properties of the enzymes as evidenced by no significant differences in K m values, inferring that it is primarily due to reduced quantities of the enzyme present in the mucosa. To determine whether this change was specific for disaccharidases, IAP-II activity was also measured because it is an inducible membrane-bound glycoprotein with a function unrelated to carbohydrate metabolism (23,41). Because IAP-II activity did not differ between the two conditions, this suggests that the decrease in sucrase and lactase activity is not due to an impaired ability of the iron-deficient enterocyte to manufacture brush border membrane glycoproteins, as previously thought (4,5,9,20,38).…”

“…The enzymatic activities of two disaccharidases, sucrase-isomaltase (su-crase) and lactase phlorizin hydrolase (lactase), were tested for both conditions as well as the activity of intestinal alkaline phosphatase (IAP)-II, because it is an inducible brush border membrane glycoprotein unrelated to carbohydrate digestion (23,41). The kinetic properties of both sucrase and lactase were also examined to confirm that any decreases result from lower quantities of enzyme present rather than due to reduced enzyme efficiencies.…”

Serum alkaline phosphatase isoenzymes in laboratory beagle dogs detected by polyacrylamide-gel disk electrophoresis

“…In addition, two staining bands corresponding to small intestinal ALP were observed at both sides of the stacking gel after anti-intestinal ALP antibody treatment. Since we collected tissue samples from duodenum and jejunum to obtain small intestinal ALP extract in the present study, there might be two intestinal ALP isoenzymes in dogs as is the case in rats (Engle and Alpers, 1992;Xie and Alpers, 2000). As a result, the zymogram of each tissue ALP extract was clear without tailing.…”