[Activity and substrate specificity of the alcohol dehydrogenases of n-alkane oxidizing yeasts]. / Aktivnost' i substratnaia spetsifichnost' alkogol'degidrogenaz drozhzhei, okisliaiushchikh n-alkany.

The activity and substrate specificity of alcohol dehydrogenases (ADH) in the fractions of cytosol and membrane particles were compared in the yeasts Torulopsis candida, Candida lipolytica and Candida tropicalis grown in media with glucose and hexadecane. In all studied yeast cultures growing in the medium with hexadecane, NAD-dependent ADH specifically dehydrogenating only medium and higher alcohols are induced in the membrane structures of the cells. Soluble ADH are found in the cytosol of the cultures grown either on glucose or on hexadecane. These ADH oxidize all alcohols with the carbon chain length from C2 to C16. As was found by electrophoresis in polyacrylamide gel, the number of ADH molecular forms in the cytosol fraction of the cultures depends on the carbon growth substrate being used and the peculiarities of yeast culture.

[Cyanide-resistant respiration in Torulopsis candida]. / Tsianidrezistentnoe dykhanie u Torulopsis candida.

The effect of cyanide and the inhibitors of cyanide-resistant oxidase--hydroxamic acids on endogenous respiration and oxidation of a number of substrates by Torulopsis candida resting cells taken at different stages of growth on glucose and hexadecane was studied and made it possible to arrive at the following conclusions. 1. The effect of cyanide on endogenous respiration of T. candida differs during its growth on glucose and hexadecane. On hexadecane, irrespective of the growth phage, cyanide inhibits endogenous respiration by 70--75%. On glucose, cyanide inhibits endogenous respiration not more than by 35% and only at the exponential growth phase whereas it stimulates endogenous respiration in the course of other growth stages. 2. The effect of cyanide on respiration of the resting cells of T. candida which oxidize glucose, hexadecane, primary alcohols and tetradecanoic acid hardly depends on the growth stage. It is determined mainly by the nature of a substrate to be oxidized. 3. Hydroxamic acid have no effect on the cell respiration in the absence of cyanide. However, in its presence, they entirely inhibit both endogenous respiration and oxidation of the aforementioned substrates. 4. Under almost all above experimental conditions, the sensitivity of cell respiration to cyanide changes only slightly at different stages of growth on either glucose or hexadecane. This feature markedly distinguishes T. candida among other cyanide-resistant yeasts.

[Alcohol dehydrogenase activity of Torulopsis candida during growth on intermediate products of glucose and hexadecane oxidation]. / Alkogoldegidrogenaznaia aktivnost' u Torulopsis candida pri ikh roste na promezhutochnykh produktakh okisleniia gliukozy i geksadekana.

The activity and substrate specificity of alcohol dehydrogenases (ADH) toward normal primary alcohols with different length of the carbon chain (C2--C16) was studied in the cells of the yeast Torulopsis candida. The yeast was grown in a mineral medium with various carbon substrates: glucose, pyruvate, acetate, hexadecane, cetol and palmite acid. Soluble ADHs in the cytosol fraction and ADHs bound to the fraction of membrane particles (mitochondria and microsomes, etc.) were found in the cells. Dehydration of higher alcohols (C8--C16) by the membrane fraction of cells was shown to have a relatively high rate (considerably higher than in cytosol) when the yeast was grown on hexadecane, cetol, palmitic acid and pyruvate. The membrane fraction of yeast cells prepared upon the growth on all carbon sources tested did not oxidize lower alcohols, ethanol and propanol. In contrast, upon the growth on glucose, ethanol and acetate the activity of ADH was mainly due to soluble ADHs and concentrated mainly in the cytosol fraction. Numerous molecular forms of ADH differing in their affinity for lower and higher alcohols and dependent on the growth substrate were revealed by electrophoresis in polyacrylamide gel.

[Alcohol dehydrogenase activity of the subcellular fractions of Torulopsis candida yeasts grown on glucose and hexadecane]. / Aktivnost' alkogol'degidrogemaz subkletochnykh fraktsii drozhzhei Torulopsis candida, vyrashchennykh na gliukoze i geksadekane.

The activity of alcohol dehydrogenase was compared in subcellular fractions of Torulopsis candida grown on glucose ("glucose cells") and on hexadecane ("hexadecane cells"). Two groups of alcohol dehydrogenases (ADH) were found to be present in the cells: (1) soluble ADH located in the cytosol and (2) ADH bound to the membrane structures and located in the mitochondria and other cell structures. Soluble ADH of "glucose cells" actively dehydrated all alcohols tested from C2 to C16. Ln "hexadecane cells", the activity was low or absent. ADH bound to the cell structures dehydrated mainly C5--C16 alcohols; the activity of these ADH was almost by an order of magnitude higher in the "hexadecane cells" as compared to the "glucose cells" (in contrast to soluble ADH). The character of changes in the activity of ADH toward various alcohols in the course of physiological adaptation of the yeast to oxidation of glucose and hexadecane suggests that both soluble and bound ADH contain at least two ADH, one of which is specific to lower alcohols and the other to higher alcohols.