Ultrastructural and anti-proteinase activity modifications of human alpha 2-macroglobulin induced by zinc and other divalent cations

Native tetrameric alpha 2-macroglobulin molecules (alpha 2M) can be converted into a population of dimers by incubation with various divalent cations such as Zn, Cd, Mg, Cu, Ni, Co. This dissociation is completed within 30 min at 37 degrees C. These dimers have a characteristic shape and a size of about 16 X 8 nm, and appear to be the half of the native alpha 2M molecule which has a clear tetrameric structure as seen in the electron microscope. At room temperature or below, dimers obtained with 5 to 100 mM Zn++ can reassociate in long linear polymers which display a regular chain-like arrangement and a helical periodicity. The structural characteristics of this polymer are described. The trypsin inhibitory capacity of Zn++-treated alpha 2M has been studied in an attempt to correlate its Zn++-induced conformational changes with its functional modifications.

Inactivation of guinea-pig serum proteinase inhibitors by Bacteroides gingivalis

The activity of proteinase inhibitors of guinea-pig serum was evaluated by using trypsin as test enzyme. Strains of black-pigmented Bacteroides species were incubated with serum under anaerobic conditions. Strains of Bacteroides gingivalis inactivated the trypsin inhibitors of guinea-pig serum within 1 h, while the other strains reduced the activity of the trypsin inhibitors by less than 50% within 48 h. The inactivation of proteinase inhibitors of guinea-pig serum by B. gingivalis may be an important pathogenic mechanism in the spreading necrotic infections induced in guinea pigs by pure cultures of this species.

Alkyl selenosulphates (seleno Bunte salts). A new class of thiol-blocking reagents

Potassium benzyl selenosulphate and potassium p-nitrobenzyl selenosulphate were shown to be powerful inhibitors of the thiol-dependent enzymes glutathione reductase and papain, but to have no effect on the serine-dependent proteinase trypsin. By contrast, potassium benzyl thiosulphate and potassium p-nitrobenzyl thiosulphate, at much higher concentrations, have virtually no effect on any of the enzymes. The selenosulphates show characteristics of both reversible non-competitive and irreversible inhibition. On the basis of model reactions in which the selenosulphates react instantly with cysteine, it is suggested that they form labile selenosulphide derivatives with the enzymes, but that these derivatives may be broken down either by the normal functioning of the enzyme (in the case of glutathione reductase) or by the approaching substrate (in the case of papain). Continued inhibition of the enzymes requires a stoicheiometric excess of inhibitor over enzyme.

On the appearance, levels and regulation of pancreatic enzyme serum concentrations

The evaluation of serum pancreatic enzyme activity on whole and diluted serum permits the estimation of serum enzyme inhibitor activity via a ADS/AWS ratio. This has diagnostic value in chronic pancreatic disease. The serum pancreatic ferment activity appears to be regulated in part by serum steroid levels. It is responsive to high protein diet. A physiologic rationale is presented for the use of steroids and high protein diet in the treatment of acute and chronic pancreatic inflammation.

Heat inactivation of trypsin inhibitor, lipoxygenase and urease in soybeans: effect of acid and base additives

Effects of chemical additives on the heat inactivation of trypsin inhibitor (TI), lipoxygenase and urease in soybeans were investigated. The nutritional value of soybeans increases when antigrowth factors, such as TI, are inactivated. Inactivation of lipoxygenase enhances palatability and storage stability. Heat inactivation of antinutritional factors during immersion cooking of dry soymeats was studied without additives. Processing time was varied from 15 min to 2 hr over a temperature range of 120–212 F. The experiments were repeated, with the addition of NaOH or HCl to the cooking water. Without additives, lipoxygenase proved to be the most heat labile and TI, the least. With either acid or base additives, the initial inactivation of urease and lipoxygenase was accelerated significantly; however, while TI inactivation was accelerated by base, it was retarded by acid addition.

Inhibitors of kallikrein in human plasma

Human plasma was fractionated by ammonium sulfate precipitation, DEAE-cellulose chromatography, and Sephadex G-200 gel filtration to determine which method would give the greatest number of clearly separable kallikrein inhibitory peaks. With G-200 gel filtration three peaks could be separated which were demonstrated to contain alpha(2)-macroglobulin, C1 inactivator, and alpha(1)-antitrypsin. No other kallikrein inhibitors could be identified. The fractions containing C1 inactivator and alpha(2)-macroglobulin appeared to be more effective against kallikrein than that containing alpha(1)-antitrypsin. A patient with hereditary angioneurotic edema was shown to have an abnormal C1 inactivator protein capable of interfering with kallikrein's biologic, but not its esterolytic activity. Heat-treated human plasma, a commonly used source of kininogen for experiments with kallikrein, was shown to have kallikrein inhibitory activity.