UNSATURATED FAT OXIDASE: DISTRIBUTION, FUNCTION AND HISTOCHEMICAL IDENTIFICATION IN PLANT TISSUES
oxidase system from naturally occurring alkalilabile inhibitols and loose addition compounds introduced (iodine, carbonic acid, etc.) into susSir taining sections. Root and stem tissues from six Tauber’ and Strain2 reported that the enzyme species of crop plants grown in buffered media at a associated with unsaturated fats in soy meal is an pH of 7.2-7.6 had a high oxidase activity in fatty “unsaturated fat oxidase.” “Carotene oxidase”3 tissues at the seedling stage, but at the end of five has been renamed “unsaturated fat oxidase” by weeks the unsaturated fat supply was very low these authors because the oxidation of carotene in and the fatty tissues were characterized by a low soy meal is a result of the enzymatic oxidation of oxidase activity and the presence of fatty degraunsaturated fat, and it is further apparent that the dational products. The reverse of this condition “lipoxidase” demonstrated earlier4J‘ is also the was obtained in the case of plants grown in same as unsaturated fat oxidase. buffered media at a PH of 4.8-5.6. Plants grown By means of some new methods of observation in relatively acid media had a higher fatty acrecorded here it is possible to confirm the work of cumulation and a low oxidase activity until Tauber and Strain and to reveal at the same time treated in section with alkaline buffered solutions. the function and intimate association of unI t is thus possible to visually isolate and activate saturated fat oxidase with specific tissues in oxidase systems in sustaining sections and in numerous crop plants. The presence of ungrowing plants by means of alkaline salts which saturated fats in microscopic preparations may be activate unsaturated fat oxidase systems but dedetected by means of Nile blue sulfate, osmium press the oxidases associated with non-fatty tetroxide, Sudan 111 and IV and Sudan black B. tissues. The oxidation and oxidase system of these fats is COLLEGE best studied by using the leuco form of methylene HEIDELBERG D. S. VANFLEET TIFFIN, OHIO blue, leuco indigo carmine, guaiacol, and ‘Wadi” RECEIVED JANUARY 27, 1943 reagent. By means of the above indicators the location and function of the unsaturated fat THE MUTAROTATION OF 6-D-ALTROSE oxidase may be demonstrated in V i e r ~ . ~ J Sir : Recent preliminary observations indicate that the unsaturated fat oxidases are activated in When D-altrose was first isolated in crystalline regions of the plant that are alkaline or neutral, form‘ we reported that mutarotation was not where water loss is taking place, beneath wound observed, the first reading being taken 3.8 minutes surfaces, and where inhibitols or antioxidants are after solution of the sugar in water at 20’. Austin absent or inactivated. Dilute solutions (0.0012- and Humoller2had reported a small mutarotation, 0.00028%) of sodium selenite, an antioxidant to [ a ] 2 0 - 2-28.75 6~ 4 -32.30’ in water, for the many respiration systems, were applied to sus- antipodal L-altrose, and accordingly had desigtaining sections and it was found that the general nated it as the ,&modification. oxidase reaction is halted and that the oxidation of With a larger amount of D-altrose now available indicators is confined to those tissues (epidermis, from the deacetylation of its a-pentaacetate, hypodermis, etc.) which have an accumulation of which was obtained by the acetolysis of 4,6unsaturated fats. Sodium selenite, as an alkaline benzylidene-a-methyl-D-a1troside, we have found salt, depressed oxidase activity in tissues (cortex that this sugar exhibits a complex mutarotation. and xylem) that are not fatty in nature and where Thus, 2.000 g. of D-altrose in 50 ml. of water the oxidases are activated only at a PH of 4.8-5.8. showed [ L Y ] ~ O D +11.7, 19.3, 25.1, 32.1 and 33.1” Sodium selenite and alkaline buffer systems ac- (final) at the end of 2.83, 4.10, 6.00, 17.8 and 31 tivated the oxidation of unsaturated fats by minutes, respectively. From calculations of the apparently freeing the lipoids and the associated velocity coefficients,derived from these and other (1) H Tauber, Tars JOURNAL, 62, 2251 (1940) intermediate measurements, it would appear that ( 2 ) H H Strain, $ b i d , 68,3542 (1941). the mutarotation consists of a very rapid inter(3) J B Sumuer and R J Sumuer, J f 3 d . C h c m , lS4, 531 -63.3 1 I M40) conversion of the furanose and pyranose modi-
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4) E. Andre and K Hon, Compt vend ,19S, 172-174 (1932) C.H Len Re+ Food Invest. Bd., Lond., 55-56 (1937) b) D.S Van Fleet, A m . J . Bot., 29, 1-15 (1942) 71 D S Van Fleet $hzd , 29, 747-7.55 (1942)
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(1) Richtmycr and Hudson, THISJOURNAL, 67, 1720 (193.5). ( 2 ) Austin and Humoller, ibid., 56, 1154 (1934). (3) Richtmyer and Hudson. ibid , 63, 1730 (1941)
