Effect of Free and Conjugated Bile Salts on α-Amylase Activity

Abstract

The effect of individual bile salts on aamylase hydrolysis of Cibachron Blue starch was studied at pH 6.0. With sodium cholate, taurocholate and taurodeoxycholate, enzyme activity was increased to 150-160% of the control value, at a concentration of ~1 mmol/1 bile salt. The increased activity extended up to 4 mmol/1. The bile salts sodium deoxycholate and taurochenodeoxycholate exerted activation and inhibition depending on the concentration. With deoxycholate (0.75 mmol/1), activation (150%) was evident, while inhibition was apparent above 2.5 mmol/1. With taurochenodeoxycholate maximum activity (135%) was observed at 0.25 mmol/1, while inhibition was evident above 1.5 mmol/1. Chenodeoxycholate and lithocholate exerted marked inhibition at concentrations as low as 0.5 mmol/1. Inhibition of a-amylase by chenodeoxycholate was competitive with both soluble and insoluble starch substrates. Since the pH of the jejunum is in the region of 6.0 the phenomenon of activation and inhibition of α-amylase by bile salts at this pH could be of physiological significance.

Effects of graded levels of medium chain triglycerides and cysteine on growth, digestive processes and nutrient utilization in sea water reared Atlantic salmon (Salmo salar, L.) underad libitumfeeding regime

“…The concomitant elevation of cysteine and taurine levels in the chyme observed in our previous experiment, indicates that MCT may also stimulate bile secretion (Nordrum et al 2000). As bile acids have the ability to activate or stabilize digestive enzymes (Malagelada et al 1973; Donnell et al 1974), stimulating effect of MCT on enzyme activity may partly be the result of increased stability. These considerations regarding the results of our previous study seem valid for the results of the present experiment as well, showing increased activities of proteolytic enzymes with increasing MCT level and higher water content of the chyme.…”

Structure of Human Salivary α-Amylase at 1.6 Å Resolution: Implications for its Role in the Oral Cavity

“…In this regard, several possible hypotheses have been put forward. It may play an anchoring role (enabling amylase to remain seated on the starch substrate) such that multiple attacks may occur (Robyt & French, 1970a,b;Thoma, Spradlin & Dygert, 1971) or it may have a regulatory function (O'Donnell, McGeeney & Fitzgerald, 1975). The second substrate-binding site between the A and C domains (Payan et al, 1980;Buisson et al, 1987) is far away from the main substrate-binding site.…”

Inhibition of Buckwheat Starch Digestion by the Formation of Starch/Bile Salt Complexes: Possibility of Its Occurrence in the Intestine

“…The rapid binding was supported by the results in Figures , , , and that bile salt-dependent inhibition of starch/iodine complex formation was observed when iodine solution was added within 1 min after the preparation of the mixture of starch and bile salts. Bile salts have been reported to be able to enhance and inhibit the amylase-catalyzed digestion at low (<1 mM) and high concentrations, respectively . The results of the present study suggest that the concentration of bile salts in bile (1–10 mM) − could inhibit starch digestion in the small intestine.…”

“…It has been reported that isoflavones bind to receptors of a steroid hormone estrogen. , The results prompted us to postulate that bile salts (Figure ) might also bind to starch to inhibit its digestion by amylase. Many studies have been conducted on the binding of bile salts to polysaccharides, − but only one study concerns the effect of bile salts on amylase-catalyzed digestion of starch …”