Cryptococcus enzyme

Despite many similarities, e.g, activation by its substrate, the Crypto-coccus enzyme is distinctly different from the wheat germ enzyme in some respects. Whereas the latter is inhibited by UDP-xylose, this compound has little effect upon the Cryptococcus enzyme, except at concentrations about 100 times greater than that of UDP-glucuronate, when 77% inhibition was observed in the experiments of Schutzbach. UDP-Glucose is a strong inhibitor of the Cryplococcus enzyme, but the type of inhibition has not been determined. 

Source of Enzyme (s) E. coli B. brevis and Agrobacterium radiobacter B. cereus, Candida bodinii Cryptococcus laurentii and Achromobacter obae P. putid,... 

The first of these enzymes has been studied the most thoroughly. Its activity has been detected in many sources, and purified preparations have been obtained from calf and beef liver,348-349 rat tissues,3498 hen oviduct,350 pea seedlings,351 Cryptococcus laurentii,352 and Aerobacter aerogenes,353 Extensive purification of the liver enzyme was achieved.349... 

In addition to its effect on enzymes, Ag has been found to produce changes in micro-organisms which may or may not be related. Thus, silver nitrate caused marked growth inhibition of Cryptococcus albicans, and was... 

For some years Foray s enzymatic process for L-lysine (L-Lys, 41) was competitive compared with fermentation. This chemoenzymatic L-Lys production was established with a capacity of 5000-10000 t/y. The key intermediate is a-amino-e-caprolactam (ACL), produced from cyclohexanone in a modified Beckmann rearrangement. The enantiospecific hydrolysis forming L-Lys is based on two enzymes L-ACL-hydrolase opens the ring of ACL to L-Lys and in the presence of the ACL-racemase the d-ACL is racemized. Incubating d,l-ACL with cells of Cryptococcus laurentii having l-ACL lactamase activity together with cells of Achromobacter obae with ACL-racemase activity, L-Lys could be obtained in a yield of nearly 100% (Scheme 24) [102]. 

Biotransformation, especially phase I metabolic reactions, cannot be assumed to be synonymous with detoxification because some drugs (although a minority) and xenobiotics are converted to potentially toxic metabolites (e.g. parathion, fluorine-containing volatile anaesthetics) or chemically reactive intermediates that produce toxicity (e.g. paracetamol in cats). The term lethal synthesis refers to the biochemical process whereby a non-toxic substance is metabolically converted to a toxic form. The poisonous plant Dichapetalum cymosum contains monofluoroacetate which, following gastrointestinal absorption, enters the tricarboxylic acid (Krebs) cycle in which it becomes converted to monofluorocitrate. The latter compound causes toxicity in animals due to irreversible inhibition of the enzyme aconitase. The selective toxicity of flucytosine for susceptible yeasts (Cryptococcus neoformans, Candida spp.) is attributable to its conversion (deamination) to 5-fluorouracil, which is incorporated into messenger RNA. 

Some microorganisms in culture show methionine-dependent ethylene formation. In studies with Escherichia coli, 2-oxo-4-methylthiobutyrate (KMB) produced from methionine by transamination was suggested as the precursor of ethylene [19], and subsequently a cell-free system which produced ethylene from KMB in the presence of NAD(P)H, EDTA-Fe and oxygen was established [20]. An enzyme which catalysed a similar ethylene-forming activity was purified from Cryptococcus albidus [15]. The purified enzyme of molecular mass 62 kDa turned out to be NADH EDTA-Fe oxidoreductase. The proposed mechanism involves reduction of EDTA-Fe to EDTA-Fe by the enzyme, reduction of oxygen to superoxide by EDTA-Fe, of hydrogen peroxide to hydroxyl radical, and oxidation of KMB by hydroxyl radical to ethylene. However, an extensive physiological evaluation of this enzyme must be done before it can... 

Cell extracts of Cryptococcus laurentii, a yeast which synthesizes amylose when grown at low pH, contain an a-D-glucan phosphorylase (EC 2.4.1.1) which has been characterized. Evidence for a possible role of this enzyme in the biosynthesis of amylose was reported. 

The stability of pectate and pectin depolymerizing enzymes produced by Mucor puriformis, Rhizopus sexualis, R. stolonifer, Botrytis cinerea, Aureobasidium pullulans, Trichosporon pullulans, and Cryptococcus albidus var. albidus in sulphite liquor has been studied in relation to the breakdown of sulphited strawberries. Marked breakdown of fruit occurred only when pectolytic activity could be detected in the liquor for more than two weeks using a viscometric assay. Of the fungi tested, Rhizopus species produced enzymes that were the most stable in sulphite liquor. For each of the Mucor and Rhizopus species tested, the stability of poly-D-galacturonases in sulphite liquor was very similar for extracts of infected fruit and culture filtrates. It was suggested that sulphite labile (=acid labile) and sulphite stable (=acid stable) forms of the poly-D-galacturonases are present. 

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