• K V Giri

      Articles written in Proceedings – Section B

    • The mechanism of β-amylase inhibition by vitamin C

      P Seshagirirao K V Giri

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      A critical study of the mechanism of β-amylase inhibition by vitamin C has been made. The hydrolysis of starch by the amylase is inhibited by vitamin C alone and vitamin C-Cu complex, the latter exerting greater inhibition.

      The oxidised products of the vitamin prepared by Cu oxidation, also exert inhibition of the hydrolysis of starch by the amylase.

      In addition to the inhibition exerted on the hydrolysis, vitamin C-Cu complex and the oxidised products of the vitamin inactivate the enzyme in the absence of substrate. Vitamin C alone brings about very feeble inactivation of the enzyme.

      A variety of compounds—oxalic acid, uric acid, xanthine, guanine, theophylline, yeast nucleic acid, creatinine, cysteine, cystine, glutathione, histidine, potassium cyanide and hydrogen sulphide, which are shown to inhibit the catalytic oxidation of vitamin C by Cu++ annul the inhibition and the inactivation caused by vitamin C, vitamin C-Cu complex and the oxidation products of the vitamin.

      A suggestive correlation between the inhibition of the hydrolysis and the inactivation of the enzyme on the one hand, and the oxidation of vitamin C on the other, has been established.

      The physiological significance of these findings in their relation to the influence exerted by the purine derivatives and other stabilisers of vitamin C oxidation in regulating the activity of amylases in plant life is discussed.

    • The inhibitors of enzymatic and cupric ion oxidation of vitamin C

      K V Giri P Seshagiri Rao

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      The influence of xanthine, adenine, uric acid, theophylline, guanine, creaturine, oxalic acid, sodium diethyldithiocarbamate and 8-Hydroxy-quinolin on the oxidation of vitamin C by Cu and ascorbic acid oxidase has been studied.

      Sodium diethyldithiocarbamate and 8-hydroxyquinolin inhibit both the enzymic and Cu oxidation of vitamin C. The other compounds investigated inhibit only the Cu oxidation without exerting any influence on the enzymic oxidation of the vitamin.

      The bearing of these results on the nature of ascorbic acid oxidase and their application to the study of the nature of catalytic systems in plants which oxidise the vitamin have been discussed. Various types of inhibitors of vitamin C oxidation have been listed and properly classified.

    • Further studies on the mechanism of β-amylase inhibition by Vitamin C

      P Seshagiri Rao K V Giri

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      The mechanism of the β-amylase inhibition by Vitamin C has been further critically examined. The observed inhibition of the hydrolysis of starch by Vitamin C alone may be due to adsorption or complex formation of the Vitamin with the substrate, the modified substrate thus formed being less easily hydrolysed than the free starch.

      Dehydroascorbic acid has no effect on the hydrolysis of starch by the amylase as well as on the enzyme in the absence of the substrate.

      Hydrogen peroxide alone does not inhibit the hydrolysis of starch, but in the presence of Cu it exerts a feeble inhibition of the hydrolysis.

      The inhibition of the amylolytic hydrolysis of starch by the oxidized products of Vitamin C by Cu oxidation, is mainly due to the traces of cuprous oxide formed during the oxidation of the vitamin.

      The protective factor present in the β-amylase is found to be undialysable and thermostable.

    • The nutritive and vitamin value of groundnut - Part I. Vitamin B1 content of groundnut (Arachis hypogea) as affected by variety

      K K Reddi K V Giri

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      Thirty-eight varieties of groundnut (Arachis hypogea) grown under identical conditions at Mysore Government Agricultural Farm, Hebbal, were analysed for their vitamin B1 content.

      Wide differences were observed in vitamin B1 content of various varieties, the value ranging from 5·4 to 17·2 micrograms per gram of defatted flour.

      No correlation between the average yields of various varieties and their vitamin B1 content was observed.

      The differences in vitamin B1 content are attributable mainly to variations in variety, as all the other conditions under which they were grown are identical.

      Other factors which influence the vitamin B1 content and the possible significance of the results obtained in the present investigation in breeding programmes are discussed briefly.

    • The nutritive and vitamin value of groundnut - Part II. The presence of free and combined forms of vitamin B1 in groundnut (Arachis hypogea)

      K K Reddi K V Giri

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      Ten varieties of groundnut were analysed for free and bound forms of vitamin B1 About 50 per cent, of total vitamin exists in the bound form.

      Digestion with papain or a mixture of papain and takadiastase have the same effect in transforming the bound vitamin into free form. The bound vitamin B1 is not a cocarboxylase.

      The bound form of the vitamin can be extracted completely, with 10 per cent. NaCl and can also be precipitated with 4 per cent, trichloroacetic acid. It, therefore, exists bound to protein.

    • The nutritive and vitamin value of groundnut - Part III. Physiological availability of vitamin B1 in groundnut (Arachis hypogea)

      K K Reddi K V Giri

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      The physiological availability of Vitamin B1 in groundnut was studied by rat growth technique. The results indicate that Vitamin B1 in groundnut is completely available for growth.

    • The nutritive and vitamin value of groundnut - Part IV. Influence of germination on the vitamin B1 content of groundnut (Arachis hypogea)

      K K Reddi K V Giri

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      The changes in vitamin B1 content of groundnut during germination were studied.

      There is decrease in total vitamin B1 content as the germination advances.

      The “bound form” of vitamin B1 is rendered free during germination.

      The probable causes for the decrease in vitamin B1 and the mechanism of transformation of “bound vitamin B1” into free form during germination are discussed.

    • The nutritive and vitamin value of groundnut - Part V. The influence of manuring on vitamin B1 content of groundnut (Arachis hypogea)

      K K Reddi K V Giri

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      The groundnut (HG1) grown in plots with various manurial treatments was analysed for vitamin B1 content by thiochrome method. No differences in vitamin B1 content were noticed, the relative values being as follows: (A) Cattle manure 14.9 micrograms/gm. of defatted flour (B)Cattle manure 14.6 micrograms/gm. of defatted flour (C) Artificial manure 14.8 micrograms/gm. of defatted flour (D) Artificial manure 14.9 micrograms/gm. of defatted flour (E) Artificial manure 14.6 micrograms/gm. of defatted flour

    • Preparation, purification and composition of pectins from Indian fruits and vegetables

      C R Krishnamurti K V Giri

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      The pectin content of a number of Indian fruits and vegetables has been estimated by four different analytical procedures using a differential extraction method.

      The conditions for the preparation of pectins from these sources have been studied.

      The structural constants like calcium pectate number, uronic anhydride, furfural and methoxyl values have been estimated.

      Jellies have been made using the pectin preparations and their strengths have been estimated.

      Attempts have been made to purify the crude pectin preparation by three different methods.

    • Influence of vitamin C and oxidising agents on prothrombin

      K V Giri P Seshagiri Rao A Rahman

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      Vitamin C, copper and vitamin C—Cu complex had no inhibitory effect on prothrombin activity, the lack of inhibition being due to the stabilization of the vitamin by the protective factors associated with the enzyme.

      While hydrogen peroxide had no effect on prothrombin activity, iodine and sodium thiosulphate were found to inactivate prothrombin, the activity in both the cases being regenerated by passing carbon dioxide. Reducing agents like sodium sulphite, however, did not regenerate the prothrombic activity lost by treatment with iodine.

      The organic solvents, chloroform and carbon tetrachloride were found to have neither activating nor inhibiting effect on prothrombin.

      The presence of traces of fibrinogen along with prothrombin appears to be necessary for the stability of the enzyme.

      The results have an important significance in throwing new light on the nature of the prothrombin and the mechanism of blood coagulation.

    • Vitamin C content of lucerne and the factors controlling its stability

      M A Sahadeo P Seshagiri Rao Sudha Deolalkar K V Giri

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      Lucerne (alfa alfa) is found to be a very rich source of vitamin C containing 1·78 mg. of the vitamin per gramme of the fresh lucerne as judged by the usual dye-titration method and Lugg’s formaldehyde method.

      Lucerne loses more than 80% of its vitamin C on drying either in direct sunlight or under the fan at 25° C.

      Lucerne contains a feeble oxidase system and a powerful protective factor, which is very thermostable and which is associated partly with the colloidal and dialysable portions of the juice.

      The protective factor is isolated free from the oxidase system and it is found to annul the non-cupric and cupric ion oxidation of vitamin C, without having any effect on the enzymic oxidation of the vitamin.

    • Interaction of Vitamin C and urease

      P Seshagiri Rao K V Giri

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      Vitamin C and Vitamin C-Cu complex inhibit urease activity, the inhibition being very marked in the latter case.

      The inhibition of urease activity of Vitamin C is not due to dehydro-ascorbic acid as the degree of inhibition produced by it is negligible compared to that produced by Vitamin C at equal concentration.

      A variety of compounds other than cysteine, like 8-hydroxy-quinoline, sodium-diethyl-dithio-carbamate and potassium cyanide, which are known to protect Vitamin C against oxidation catalysed by Cu++, are shown to protect the urease from inactivation by Vitamin C and Vitamin C-Cu. showing that the inactivation of urease by Vitamin C is related to the oxidation of the vitamin.

      A well marked correlation between the inactivation of urease on the one hand and the oxidation of Vitamin C on the other has been established.

      It is suggested that the inactivation of urease by Vitamin C catalyzed by Cu++ may be due to any intermediate products like Cu2O formed during the oxidation.

    • A micro-electrophoretic study of human serum proteins in small-pox

      M A Cohly K V Giri M R A Rao

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      An electrophoretic analysis of normal and small-pox human sera has been carried out employing Kern’s micro-electrophoretic apparatus using Michaelis buffer of pH 8·6 and ionic strength μ=0·1. The results indicate that the pathological condition brings about an increase in all the globulin fractions and a decrease in the albumin moiety.

    • A blood anticoagulant factor from the latex ofCarica papaya - Part I. Purification and general properties

      N C Pillai C S Vaidyanathan K V Giri

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      A factor capable of effectively inhibiting the process of coagulation of plasma as well as whole blood has been isolated from the latex ofCarica papaya. Attempts were made at purification of the factor by adsorption and fractional precipitation with organic solvents. A comparatively pure product was obtained by cold acetone fractionation at a final concentration of 42 to 48%. It was found that there was no correlation between the residual proteolytic activity and the anticoagulant property of the factor. Some of the general properties of the anticoagulant factor have also been studied.

    • A blood anticoagulant factor from the latex ofCarica papaya - Part II. Its nature of action on blood coagulation

      N C Pillai C S Vaidyanathan K V Giri

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      A detailed investigation has been carried out on the mode of action of the anticoagulant factor present in the latex ofCarica papaya.

      The dual function of the anticoagulant factor,viz., the inhibition of the conversion of prothrombin to thrombin, and the destruction of thrombin activity has been established.

      It has been found that the iodacetate treatment destroys the antithrombin activity of the anticoagulant factor. However, the iodacetatetreated anticoagulant factor inhibits the formation of a perfect fibrin clot from plasma, even in the presence of active thrombin, probably through complex formation with the fibrinogen of the plasma. The possibility of the presence of a co-factor in plasma which promotes this complex formation is also envisaged.

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