scholarly journals Constancy of the optimum temperature of an enzyme under varying concentrations of substrate and of enzyme

In a recent paper a new enzymic relation is recorded. For the enzymic hydrolysis of salicin—by the enzyme which Gabriel Bertrand and the author have named salicinase —it is found that, in an action of fixed duration, the temperature of greatest activity of the ferment is always the same, whatever the dilutions of substrate and of enzyme adopted for the determination. In other words, the duration of the action being constant, the optimum tem­perature of the ferment is independent of the concentration both of the substrate and of the enzyme. The observation is suggestive: if true of one enzyme it may be true of all, and possibly becomes the enunciation of a general law. Herein, for the moment, lies its main interest. In the present paper further experimental evidence for this hypothesis in given, in the case of another hydrolytic enzyme, the maltase of Aspergillus oryzæ (taka-diastase).

1880 ◽  
Vol 26 (113) ◽  
pp. 119
Author(s):  
B. F. C. Costelloe

The first number for the year is not remarkable for any paper of striking value. Readers of the Journal will be chiefly attracted by the long and clearly written resumé of Dr. Hughlings Jackson's recent studies “On Affections of Speech from Disease of the Brain,” which is contributed by Mr. James Sully. He remarks on the great value of Dr. Jackson's attempts to classify the different forms of aphasia under the three main heads or stages of—(1) Defect of Speech, in which the patient has a full vocabulary, but confuses words; (2) Loss of Speech, in which the patient is practically speechless, and his pantomimic power is impaired as well; and (3) Loss of Language, in which, besides being speechless, he has altogether lost the power of pantomime, and even his faculty of emotional language is deeply involved in the wreck. All these states or stages again are, properly speaking, to be distinguished altogether from affections of speech in the way of loss of articulation (owing to paralysis of the tongue, &c.), or loss of vocalisation (owing to disease of the larynx); whereas the three degrees or stages of aphasia proper are due to a deep-seated and severe disorganisation of the brain. The main interest of the theory lies in the ingenious and carefully-argued analysis of the symptoms, by which Dr. Jackson arrives at the theory that as the process of destruction goes on, the superior “layers” or strata of speech fail first—those namely which involve the ordinary power of adapting sounds to the circumstances of the moment as they arise; after them fail the “more highly organized utterances” those, namely, which have in any way become automatic, such as “come on,” “wo! wo!” and even “yes” and “no,” which stand on the border-line between emotional and intellectual language; next fails the power of adapting other than vocal signs to convey an intended meaning, which is called, rather clumsily, “pantomimic propositionising;” and last of all dies out the power of uttering sounds or making signs expressive merely of emotion—a power which, of course, is not true speech at all.


1963 ◽  
Vol 46 (2) ◽  
pp. 341-343
Author(s):  
M Alice Brown ◽  
James R Woodward ◽  
Floyd DeEds

Abstract The amount of naturally occurring methanol in fruit must be known so that the quantity left as fumigation residue can be determined. In a study of methanol content of raisins, which had given inconsistent results, the raisins were subjected to different conditions of treatment immediately prior to methanol determination. Conditions that favored pectin esterase activity gave higher values for methanol content than conditions known to inactivate enzymes. Evidence was also obtained that both chemical and enzymic hydrolysis of methyl ester groups of pectic materials occur during analysis.


1975 ◽  
Vol 64 (3) ◽  
pp. 586-607 ◽  
Author(s):  
N Simionescu ◽  
M Siminoescu ◽  
G E Palade

Two heme-peptides (HP) of about 20-A diameter (heme-undecapeptide [H11P], mol wt approximately 1900 and heme-octapeptide [H8P], mol wt approximately 1550), obtained by enzymic hydrolysis of cytochrome c, were sued as probe molecules in muscle capillaries (rat diaphragm). They were localized in situ by a perixidase reaction, enhanced by the addition of imidazole to the incubation medium. Chromatography of plasma samples showed that HPs circulate predominantly as monomers for the duration of the experiments and are bound by aldehyde fixatives to plasma proteins to the extent of approximately 50% (H8P) to approximately 95% (H11P). Both tracers cross the endothelium primarily via plasmalemmal vesicles which become progressively labeled (by reaction product) from the blood front to the tissue front of the endothelium, in three successive resolvable phases. By the end of each phase the extent of labeling reaches greater than 90% of the corresponding vesicle population. Labeled vesicles appear as either isolated units or chains which form patent channels across the endothelium. The patency of these channels was checked by specimen tilting and graphic analysis of their images. No evidence was found for early or preferential marking of the intercellular junctions and spaces by reaction product. It is concluded that the channels are the most likely candidate for structural equivalents of the small pores of the capillary wall since they are continuous, water-filled passages, and are provided with one or more strictures of less than 100 A. Their frequency remains to be established by future work.


Biochemistry ◽  
1969 ◽  
Vol 8 (12) ◽  
pp. 4716-4723 ◽  
Author(s):  
Howard B. Bensusan

1979 ◽  
Vol 27 (5) ◽  
pp. 1098-1104 ◽  
Author(s):  
Antoine J. Puigserver ◽  
Lourminia C. Sen ◽  
Elvira Gonzales-Flores ◽  
Robert E. Feeney ◽  
John R. Whitaker

1986 ◽  
Vol 18 (2) ◽  
pp. 103-109 ◽  
Author(s):  
Tomoko Komiyama ◽  
Takayasu Mori ◽  
Hajime Omata ◽  
Makoto Miwa

1995 ◽  
Vol 9 (7) ◽  
pp. 623-628 ◽  
Author(s):  
N. Gilon ◽  
A. Astruc ◽  
M. Astruc ◽  
M. Potin-Gautier

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