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In this work on Rhodotorula gracilis, we studied the level of the representative enzymes of foundamental metabolic ways (HK, PK, G6PDH and IDH) and those of ICL and MS key enzymes of glyoxylate cycle with different carbone sources. The glucose appears the best source of carbone for all the tested enzymes except ICL and MS which are practically absent in the cells developed with this carbone source. In presence of acetate and ethanol we have obtained the expression of the glyoxylate cycle enzymes (ICL and MS). Moreover we obtained the operativity of the glyoxylate cycle in the lipid-rich cells or cells developped on neutral detergents or anionics similar to the fatty acids.

We studied the effect of L-lactate on both the cleavage and the condensation reactions of Pinus pinea isocitrate lyase. This compound is a competitive of Pinus pinea isocitrate lyase towards both isocitrate and glyoxylate, whereas is a mixed type inhibitor towards succinate. Assuming that L-lactate acts as a glyoxylate analogue, our finding agrees with an uni-bi ordered mechanism of isocitrate lyase, with glyoxylate first substrate to enter the active site in the condensation reaction. Results are discussed and compared with those known in the literature about other structurally related metabolites.

We describe here the effects of natural and synthetic detergents on the D-glucose transport into brush-border membranes of vesicles of rabbit's intestine. Two synthetic detergents: Triton X-100 and dodecyltrimethylammonium bromide have been found very strong inhibitors (more than 50 p. 100 of inhibition of maximal D-glucose uptake). Kinetic studies showed that these detergents behaved as mixed type inhibitors. The Na+-dependent transport of amino acids (aspartic acid, lysine, phenylalanine) is only poorly affected by dodecyltrimethylammonium bromide, while Triton X-100 inhibits unspecifically all the transport studied.

Neutral maltase from human granulocytes has a different substrate specificity from the human neutral maltase of kidney, though it has been reported that these two enzymes are immunologically similar. We report here that human granulocyte neutral maltase is similar to the neutral maltase from rat's kidney as regards the substrate specificity and the inhibition by Tris and maltodextrins. We also report a different thermal stability that might imply some structural differences between the two enzymes.