Alcohol dehydrogenase, in Drosophila melanogaster homozygous for the alleles Adh(F) or Adh(S), is found in three electrophoretically different forms. Adh' differs from Adh(5) in that isozymes with faster electrophoretic mobilities are present. In Adh(F)/Adh(S) heterozygotes, hybrid isozymes as well as the parental isozymes are present, indicating that the dehydrogenase may exist as a dimer of two polypeptide subunits. The gene, Adh, is located on the second chromosome, with a map position of 50.1 and a cytological position between 34E3 and 35D1.

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Horseradish peroxidase has been used to generate iodine compositions that comprised principally free molecular iodine. The concentration of free molecular iodine in these enzyme-based compositions ranged from 44 to 63% of the thiosulphate titratable iodine; this is substantially higher than the corresponding value for the povidone-iodine preparation betadine. The biocidal efficacy of these compositions was proportional to the concentration of free molecular iodine. Iodine compositions with relatively low total iodine concentrations but high levels of free molecular iodine (20-175 ppm) killed Staphylococcus aureus and spores of Bacillus subtilis more rapidly than betadine. The effects of normal saline and these enzyme-based iodine compositions on the rate of epidermal regeneration in superficial swine wounds were comparable. These results suggest that an effective germicide containing a high level of molecular iodine need not be irritating or toxic.

Cacodylic acid is an arsenical with the structural formula HOAsO(CH,),. Since its pKa is 6.15, cacodylic acid is often used along with an appropriate cation to buffer enzyme-catalyzed reactions. We report here that cacodylic acid reacts with various SH-containing materials that are commonly used in enzyme-catalyzed reactions, such as 2-mercaptoethanol, cysteine, glutathione, and dithiothreitol. When cacodylate and these alkyl thiols are present together they may be expected to react spontaneously and thus interfere with the study of other reactions either by depleting the amount of these substances or by producing a product that is inhibitory.

. Can. J. Chem. 52, 2648 (1974).A series of para-substituted 0-benzoyl-2-hydroxybutanoic acids (but not the unsubstituted ester) are hydrcijred by bovine carboxypeptidase A ( p H 7.5, ionic strength 0.5, 25"), For the CH,O, CH,, CI, CN, and NO2 substituents, there exist linear correlations of kc,, and K,,, with the Hammett o constants for these substituents (log kc,, = 1.170 f 1.17; log K,,, = -0.530 -2.15), although the tert-butyl group shows significant deviations from both correlation lines. The above unsubstituted ester is a reversible inhibitor of the enzymic hydrolysis of 0-hippuryl-L-3-phenyllactic acid and so the lack of observable hydrolysis of this ester is attributable to nonproductive binding. The pH-rate profiles for k,,,/K, and kc,, have been determined for the enzymic hydrolysis of 0-(p-nitrobenzoy1)mandelic acid (pKEH, = 6.95, pKEH = 7.9 and pKEH2, = 7.5, pKEHs = 8.3) and 0-hippuryl-L-3-phenyllactic acid (pKEH, = 5.8, pKEH = 9.3). For the latter ester kc,, is p H independent in the range p H 5-10. The mechanisrn of ester hydrolysis catalyzed by carboxypeptidase A is discussed in the light of the above observations and the known crystal structure of the enzyme. A definition of specific and nonspecific substrates for this enzyme based on the observed p H profiles for k,,,/K,,, is proposed. 52, 2648 (1974).Des series d'acides 0-benzoyl hydroxy-2 butanoi'ques substitues en para (rnais pas les esters non substitues) sont hydrolyses par la carboxypeptidase A du bovin (pH 7.5, 25', force ionique de @.5). I1 existe des correlations lineaires entre k,,,, K,,, et les constances o de Hammett des substituants CH,O, CH,, C1, C N et NO, (log kc,, = 1.170 + 1.17; log K,,, = -0.530 -2.15).Toutefois le groupe revt-butyle montre des deviations significatives de ces deux droites de corrClations. L'ester non substitut ci-dessus est un inhibiteur reversible de I'hydrolyse enzym a t i q~~e de I'acide 0-hippuryl phenyl-3 L-lactique, et ainsi on n'observe pas d'hydrolyse de cet ester a cause d'une liaison non-reactive. On determine la courbe de p H pour k,,,/K, et kc,, 10: s de I'hydrolyse enzymatique de I'acide 0-(p-nitrobenzoyl) niandelique (pKEH2 = 6.95, PKE" = 7.9 et pKEH2, = 7.5, pKrHs = 8.3) et de l'acide 0-hippuryl phenyl-3 L-lactique (pKEH2 = 5.8, pKEH = 9.3). Pour ce dernier ester, kc,, reste constant pour une variation du p H de 5-10. A la lumiere de ces observations et de la structure connue du cristal de l'enzyme, on discute du mecanisme de I'hydrolyse des esters catalysee par la carboxypeptidase A. On propose une definition des substrats specifiques et non-specifiques pour cette enzyme, basee sur I'observaticn des courbes de p H pour k,,,'K,,,.[Traduit par le journal]During the past few years, evidence has accumulated that the y-carboxyl group of glutamic acid residue 270 plays a role in the mechanism of hydrolyses catalyzed by bovine carboxypeptidase A. Lipscomb and co-workers (1-4), based on their X-ray crystallographic investigation of the structure of this enzyme, originally suggested that this carboxyl...