Active-site studies on rabbit liver nicotinamide deamidase

Enzymology of Nad + Synthesis

“…The mammalian enzyme was also found to possess broad esterase activity with a remarkable affinity for pyridine ring-containing esters, whose Km values are lower than that for nicotinamide (Su et al, 1969). The esterase activity shows a pH optimum that is higher than that of the deamidase activity (Albizati and Hedrick, 1972). While the latter activity requires both reactive serine and histidine residues, the former activity requires only serine residues (Albizati and Hedrick, 1972;Gillam et al, 1973).…”

“…The esterase activity shows a pH optimum that is higher than that of the deamidase activity (Albizati and Hedrick, 1972). While the latter activity requires both reactive serine and histidine residues, the former activity requires only serine residues (Albizati and Hedrick, 1972;Gillam et al, 1973). The cytoplasmic nicotinamide deamidase form was found to be released in the growth medium of several tissue cultures (Wintzerith et al, 1979).…”

“…The fraction of 218,000 M, used for the characterization is a glycoprotein containing 2.84% mannose and 0.57% glucosamine, consisting of four subunits of 60,000 MI (Su and Chaykin, 1971;Gillam et al, 1973). It is inhibited by a large variety of compounds, including fatty acids present in liver homogenates (Greengard et d., 1969;Gillam et al, 1973), thyroxine, which causes the disruption of the enzyme structure (Gillam et al, 1973), and the site-specific reagents DFP (diisopropylfluorophosphate) and ZPCK (carbobenzoxyamido-2-phenylethyl chloromethyl ketone), thus implicating the presence of seryl and histidil residues in the active center (Albizati, and Hedrick, 1972;Gillam et al, 1973). The pH optimum of the partially purified enzyme was found to be strongly dependent on the concentration of nicotinamide (Su et al, 1969).…”

“…The presence in the enzyme preparation of contaminating lipid material, which affects the kinetic behavior of the enzyme, makes it difficult to ascertain definitively whether the protein has allosteric properties. Nevertheless, K , values ranging from 20 to 250 mM have been reported for nicotinamide (Kirchner et al, 1966;Albizati and Hedrick, 1972;Gillam et al, 1973). NAD+ has no effect on deamidase activity, whereas nicotinate was found to be a competitive inhibitor (Su et al, 1969).…”

Chemical modification of acetylcholinesterase from eel and basal ganglia: effect on the acetylcholinesterase and aryl acylamidase activities

“…An interesting feature of the AAA associated with AChE is its sensitivity to inhibition specifically by serotonin (Fujimoto, 1974(Fujimoto, , 1976Oommen & Balasubramanian, 1977).The bifunctional nature of AChE is analogous to the esterolytic and amidolytic activities exhibited by several known enzymes such as chymotrypsin, trypsin, carboxypeptidase A, elastase, and thrombin. In many of these enzymes, evidence is available for nonidentical active centers2 for the esterolytic and amidolytic activities (Albizati & Hedrick, 1972;Simpson et al, 1963; Colletti-Previero et al, 1969).We have undertaken a study of amino acid modification of AChE from electric eel and sheep basal ganglia for identifying the active centers of AChE and AAA. The involvement of serine, tryptophan, tyrosine, and histidine residues in either the esteratic site or the peripheral anionic site of AChE has been indicated by earlier workers [see review of Rosenberry…”