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Sulfate-activation, enzymes

Finally, a precise clinical use of pregnenolone sulfate can be considered since this compound seems to be active in depressing uterine contractility, without being previously transformed into progesterone (Scom-megna et al, 1970). With respect to possible hormonal control of cancer, Libby and Dao (1970) have indicated that certain breast tumors, which do not regress after adrenalectomy, lack sulfate-activating enzymes. [Pg.181]

Molybdate is also known as an inhibitor of the important enzyme ATP sulfurylase where ATP is adenosine triphosphate, which activates sulfate for participation in biosynthetic pathways (56). The tetrahedral molybdate dianion, MoO , substitutes for the tetrahedral sulfate dianion, SO , and leads to futile cycling of the enzyme and total inhibition of sulfate activation. Molybdate is also a co-effector in the receptor for steroids (qv) in mammalian systems, a biochemical finding that may also have physiological implications (57). [Pg.475]

Purification. Enzyme purity, expressed in terms of the percent active enzyme protein of total protein, is primarily achieved by the strain selection and fermentation method. In some cases, however, removal of nonactive protein by purification is necessary. The key purification method is selective precipitation of the product or impurities by addition of salt, eg, sodium sulfate, or solvent, eg, ethanol or acetone by heat denaturation or by isoelectric precipitation, ie, pH adjustments. Methods have been introduced to produce crystalline enzyme preparations (24). [Pg.290]

If the cell is well supplied with nutrients, then the production of activated enzyme is great and this step is relatively fast. If the transport of sulfate into the cell cannot keep up with the reduction of sulfate, the concentration of sulfate within the cell becomes small, and very little of the isotopically fractionated sulfate inside the cell can leak back out of the cell. Thus, the effect of the internal isotopic fractionation on the outside world is minimal and the overall fractionation of the process is small. In a hypothetical extreme case, every sulfate anion entering the cell would be consumed by reduction. This would require a complete lack of isotopic fractionation, because when all S atoms entering are consumed, there can be no selection of light vs. heavy isotopes. The isotopic fractionation of the overall reduction reaction would be equal to that which occurs during the diffusion step only. [Pg.298]

This enzyme [EC 2.8.2.15] catalyzes the reaction of 3 -phosphoadenylylsulfate with a phenolic steroid to produce adenosine 3, 5 -bisphosphate and a steroid O-sulfate. The enzyme is very similar in its activity to alcohol sulfotransferase. However, steroid sulfotransferase can utilize estrone as a substrate. [Pg.657]

Minoxidil (Loniten) is an orally effective vasodilator. It is more potent and longer acting than hydralazine and does not accumulate significantly in patients with renal insufficiency. It depends on in vivo metabolism by hepatic enzymes to produce an active metabolite, minoxidil sulfate. Minoxidil sulfate activates potassium channels, resulting in hyperpolarization of vascular smooth muscle and relaxation of the blood vessel. [Pg.229]

Figure 1. Elution patterns of the ammonium sulfate-precipitated enzyme preparation from a DEAE-Sephadex A-50 column. (0) CMC-saccharifying activity (5-min incubation) of eluates diluted 60-fold, (O) Avicel-saccharifying activity (1-hr incubation), ( ) protein concentration measured in terms of the absorbance at 280 nm column 5.0 X 50 cm flow rate 20 mL/8 min one fraction 20 mL. Figure 1. Elution patterns of the ammonium sulfate-precipitated enzyme preparation from a DEAE-Sephadex A-50 column. (0) CMC-saccharifying activity (5-min incubation) of eluates diluted 60-fold, (O) Avicel-saccharifying activity (1-hr incubation), ( ) protein concentration measured in terms of the absorbance at 280 nm column 5.0 X 50 cm flow rate 20 mL/8 min one fraction 20 mL.
Manganese is essential for the synthesis of chondroitin sulfate, a mucopolysaccharide which is an important component of bone cartilage. Manganese is also required to activate enzymes involved in the synthesis of polysaccharides and... [Pg.40]

Subtilisin BPN was prepared through a series of protein purification steps applied to the fermentation broth. These steps included ultrafiltration ethanol precipitation DEAE (diethyl-aminoethyl) Tris Acryl batch anionic exchange SP (sulfopropyl) Tris Acryl column cationic exchange and, concentration with an Amicon stirred cell. The enzyme purity was determined to be -951 via spectroscopic assays that measure the ratio of active enzyme to total protein. In addition, purity was verified via HPLC and SDS-page (sodium dodecyl sulfate polyacrylamide gel electrophoresis). [Pg.227]

Metal Ion Effects. The metal ion effects on the acid-catalyzed hydrolysis of PPS also were examined by Benkovic and Hevey (5). However, they observed that in water near pH 3, the rate enhancement in the presence of an excess of metal ion was at most only threefold (Mg2+, Ca2+, Al3+) and in some cases (Zn2+, Co2+, Cu2+) the rate was actually retarded. We thought that the substrate PPS and Mg2+ ion should be hydrated heavily in water so that their complexa-tion for rate enhancement is weak. If, however, the hydrolysis is carried out in a solvent of low water content, such complexation would not occur, and therefore, the rate enhancement might be more pronounced. This possibility appears to be supported by the fact that the active sites of many enzymes are hydrophobic. Of course, there is a possibility that the S—O fission may not require metal ion activation. In this connection, it is interesting to note that in biological phosphoryl-transfer reactions the enzymes generally require divalent metal ions for activity (7, 8, 9), but such metal ion dependency appears to be less important for sulfate-transfer enzymes. For example, many phosphatases require metal ions, but no sulfatase is known to be metal... [Pg.408]

Several membrane-bound ATPases occur in the genus Sulfolobus. There are two ATP-hydrolyzing activities in S. acidocaldarius strain 7. One has a pH optimum at 6.5 in the absence of sulfate, and the presence of that anion activates the enzyme and shifts the pH optimum to 5.0. ATP hydrolysis is unaffected by DCCD, azide, NEM, /7-hydroxymercuribenzoate, or vanadate [59]. The other ATPase is most active at pH 2.5, is inhibited by sulfate, and appears to be a pyrophosphatase [16]. The purified sulfate-activated ATPase (M, 360000) is composed of three subunits (Mr 69000, 54000, and 28000). It is most active at 85 C, stimulated some three-fold by sulfate, sulfite, and bicarbonate, but is unaffected by chloride. There are two pH optima. One is located at pH 5 and the other at pH 8.5 and neither is affected by sulfite. ATPase activity is inhibited by nitrate (63% at 20 mM) and NBD-Cl (90% at 1 mM) but is not significantly affected by azide (5mM), vanadate (100 pM), and NEM (100pM)[28]. [Pg.302]

The differences in the motion of the two loops seen in the simulations appeared to originate from differences between the two subunits in the crystal structure that made the closing of the loop in subunit II less probable than in subunit I. These seemed to hinder full relaxation of all the bonds and angles in the loop in subunit II to their equilibrium values, so that, during much of the simulation time, only 9 residues moved in subunit II, whereas 11 moved in subunit I. This discrepancy appears to arise from crystal contacts, which keep the loop in subunit II in a defined open conformation in the crystal structure, whereas the loop in subunit I is disordered and exposed to solvent. Sulfate and phosphate ions are able to bind in the active site of subunit I but not subunit II in the crystal. These differences suggest that the loop in subunit I may undergo motions that are more representative of those of the active enzyme in solution than the loop in subunit II, which exists in a somewhat artificial state that restricts its motion. Therefore, the effect of gating on the rate constant of the reaaion was estimated from the motion of the loop in subunit I. [Pg.260]


See other pages where Sulfate-activation, enzymes is mentioned: [Pg.318]    [Pg.318]    [Pg.342]    [Pg.364]    [Pg.222]    [Pg.298]    [Pg.299]    [Pg.162]    [Pg.334]    [Pg.337]    [Pg.339]    [Pg.127]    [Pg.410]    [Pg.159]    [Pg.1722]    [Pg.510]    [Pg.420]    [Pg.89]    [Pg.161]    [Pg.316]    [Pg.958]    [Pg.259]    [Pg.630]    [Pg.11]    [Pg.296]    [Pg.312]    [Pg.171]    [Pg.339]   


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