Sumner group

Enzymes may be described a organic catalysts of biological origin. The majority are obtained from the interior of cells, but some are obtained from natural secretions such as the digestive juices and milk. For a full discussion of the nature of enzymes and the mechanism of their reactions the student should consult a work such as Chemistry and Methods of Enzymes, by J. B. Sumner and G. F. Somers (Academic Press, New York), or Enzymes, by M. Dixon and E. C. Webb[(Longman Group Ltd.). The following points should however be noted ... 

The title retains the trivial name for enzymes with the systematic name of urea amidohydrolase and the Enzyme Commission code number of EC 3.5.1.5. Ureases are hydrolases acting on C-N bonds (nonpeptide) in linear amides and thus belong to a group that includes glutaminase, form-amidase, and formyltetrahydrofolate deformylase. The title is plural to emphasize that urease activity may be exhibited by several protein species. Urease, singular, has come to mean by common usage, that particular enzymic protein first crystallized by Sumner from jack bean... 

The isoelectric point, determined by Sumner and Hand (50) to have a value of 5.0-5.1, has been redetermined by the electrofocusing technique (43). The value obtained was 4.8. The solubility is extremely small at this pH, but the urease can be located by its enzymic action. It is a point of interest that the solubility of the isoelectric species increases spectacularly if the sulfhydryl groups are substituted with A-ethylmaleimide (NEM) (43). 

As noted above, Sumner and co-workers were unable to determine the diffusion coefficient of urease unless they added Na2S03 and NaHSO-to the phosphate buffer (40) used. Nichol and Creeth, employing identical concentrations (60), measured both the sedimentation coefficient and the electrophoretic mobility of sulfite-modified urease. They concluded that sulfite contributed to the formation of -S-S03 groups attached to the (16n) species. Some of these groups they ascribed to the scission of intermolecular disulfide bonds of aggregated forms others, they suggested, arose from the 22 reactive sulfhydryl groups that react with 02 (air) to form transitory disulfides that can, in turn, react with sulfite. 

Horseradish peroxidase (and urease) played an important role in the development of the modern concept of the nature of an enzyme and the role of metal ions (Sumner and Somers, 1943 Willstatter, 1965). The species now known as compound II (HRP-II) formed as a result of the reaction of HRP with H202, was discovered in 1937 (Keilen and Mann, 1937). Later compound I (HRP-I), formed prior to HRP-II was identified (Theorell, 1941). The spectra of HRP-I and HRP-II in the 400 nm (Soret band) region have been determined (Chance, 1949 a, b) and measurements have also been extended to the visible region (Chance, 1952). Formation of HRP-I is first order in H202 and HRP (Chance, 1943) and the -OOH group is essential for the oxidation of HRP by peroxide. The enzymatic cycle can be summarised by the following equations (George, 1952),... 

A. C. Cleves, J. F. Sumner, R. M. H. Wyatt, in Proceedings of the Third Conference on Static Electrification, D. K. Davies, ed.. Static Electrification Group, Institute of Physics. London, 1971. 

Through the first quarter of this century. .. the most important group of macromolecules was believed to be the proteins. .. [the discovery by Sumner that enzymes were proteins] did not dispel the general aura of mystery about proteins. .. it was still possible as late as 1940, for some scientists to believe that these molecules would eventually be shown to have features unique to life... (Watson, 1976, pp. 25 6)... 

Guarner J, Sumner J, Paddock CD, et al. Diagnosis of invasive group A streptococcal infections by using immunohistochemical and molecular assays. Am J Clin Pathol. 2006 126 148-155. 

Sumner LW, et al. Proposed minimum reporting standards for chemical analysis Chemical Analysis Working Group (CAWG) Metabolomics Standards Initiative (MSI). Metabolomics 2007 3 211-221. 

Both Gjessing and Sumner (57) and Theorell et al. (221) have tried the effect of splitting the protoheme from the glob in and replacing it with a variety of other hemes. Only meso- and deuterohemes gave compounds which are catalytically active, although combination occurred with all the hemes tried except hematoheme. It thus appears that activity is dependent on the presence of two propionyl groups in the heme in positions 6 and 7. 

Since 1900, enzyme research has developed to such an extent that each single enzyme or a single property of a class of enzymes has proved sufficient to engage the attention of a group of investigators. Important dates are 1926, ciystallisation of urease (Sumner) 1932, discovery of flavin enzymes (Warburg) 1933, isolation of the co-enzymes 1935, isolation of virus protein (Stanley). 

From variations in the composition of their preparations Willstatter and Waldschmidt-Leitz have been led to a bearer theory of enzyme structiue, according to which each enzyme consists of (1) a colloidal bearer, usually of protein nature, and (2) one or more active groups which enable the bearer to become affixed to the substrate. The distinction between the soluble lyo-enzymes and the insoluble desmo-enzymes is determined by the solubility of the protein bearer. Sumner and Northrop, however, maintain that the crystalline enzymes are pure proteins, and that even partial hydrolysis of the protein destroys the enzyme. While, of course, it is possible that both theories may be true in that they apply to different enzyme types, the balance of evidence supports the conclusions of the American workers, and leads to the recognition of a new class of biochemical compounds, the zymo-proteins. 

As may be seen in Table I (page 266), several new catalases have been crystallized in the last years. The active group in catalases is proto-hematin (Zeile and Hellstrom, 94 Stem, 58). In addition to this some catalases contain a blue component which is split off by treatment with acetone and hydrochloric acid. Stem, who described the blue product first, believed it to be an impurity, whereas Sumner and Dounce (62) reported it to be a decomposition product of pure catalase. Lemberg, Norrie, and Legge (49) crystallized it and defined it as biliverdin. 

---