Portal de Periódicos da CAPES

Effects of Roentgen Rays on the Activation and Production of the Enzyme Tyrosinase in the Insect Egg (Orthoptera)

1938; Radiological Society of North America; Volume: 31; Issue: 4 Linguagem: Inglês

10.1148/31.4.428

1527-1315

O. Malcolm Ray,

Insect and Pesticide Research

Introduction MOST investigations on radiant energy in relation to enzymes indicate that enzymes are affected by various types of radiations. Sunlight and ultraviolet radiation have been used extensively and result, for the most part, in varying degrees of inactivation with an occasional report of stimulation (Duggar, 8). The situation in regard to the effects of roentgen rays is similar. Inactivation, more or less resembling the effects of heat, is often reported (Clark and Northrop, 7). In a few instances, acceleration has been obtained by short exposures, with inactivation only after extensive x-irradiation (Richards, 15). The action of radium rays on digestive enzymes has been investigated and found to result in destruction of their activity (Henri and Mayer, 10). Experimental studies on the effects of visible and ultra-violet rays on the enzyme, tyrosinase, demonstrate that it also is altered by irradiation. In two instances it has been reported that the activity of this enzyme was greatly reduced by exposure to ultra-violet rays (Pincussen and Hammerich, 13; Agulhon, 1). It has also been shown (Agulhon, 2; Przibram and Dembowski, 14) that visible light destroys tyrosinase only in the presence of oxygen, and it is suggested (Przibram and Dembowski, 14) that the destruction may be due to the formation of hydrogen peroxide, inasmuch as ultra-violet rays do not destroy the enzyme's activity when it is dissolved in glycerin. In more recent investigations (Narayanamurti and Ayyar, 11; 12) the slightly increased activity after ultra-violet irradiation is explained as being due to a decrease in the negative charge of the enzyme permitting increased adsorption catalysis. It has also been shown (Willcock, 17) that tyrosinase is an exception to the rule in that it is not affected by exposure to beta and gamma rays of radium. In view of these considerations it was thought that the effects of roentgen radiations on tyrosinase might be of interest, and it is the purpose of the present paper to present results of a study on the effects of roentgen rays on the activity of the enzyme and on its production in the developing orthopteran egg. Material and Methods Several features that make the eggs of the grasshopper, Melanoplus differentialis, desirable for use in an investigation of this kind have previously been pointed out (Bodine, 3). The effects of roentgen irradiation on both tyrosinase solutions and eggs were determined. Eggs of varying ages throughout both developmental periods (pre-diapause and post-diapause of 18 days each) as well as during the intervening inactive period (three to four months at 0° C.) were irradiated. The preparation of the enzyme solution was similar to that of Bodine, Allen, and Boell, (5).