Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.4.21.4 (trypsin)
 42,187 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Yeast acyl-coenzyme A:dihydroxyacetone-phosphate O-acyltransferase (DHAP acyltransferase; EC 2.3.1.42) was investigated to (i) determine whether its activity and that of acyl-coenzyme A:sn-glycerol-3-phosphate O-acyltransferase (glycerol-P acyltransferase; EC 2.3.1.15) represent dual catalytic functions of a single membranous enzyme, (ii) estimate the relative contributions of the glycerol-P and DHAP pathways for yeast glycerolipid synthesis, and (iii) evaluate the suitability of yeast for future genetic investigations of the eucaryotic glycerol-P and DHAP acyltransferase activities. The membranous DHAP acyltransferase activity showed an apparent Km of 0.79 mM for DHAP, with a Vmax of 5.3 nmol/min per mg, whereas the glycerol-P acyltransferase activity showed an apparent Km of 0.05 mM for glycerol-P, with a Vmax of 3.4 nmol/min per mg. Glycerol-P was a competitive inhibitor (Ki, 0.07 mM) of the DHAP acyltransferase activity, and DHAP was a competitive inhibitor (Ki, 0.91 mM) of the glycerol-P acyltransferase activity. The two acyltransferase activities exhibited marked similarities in their pH dependence, acyl-coenzyme A chain length preference and substrate concentration dependencies, thermolability, and patterns of inactivation by N-ethylmaleimide, trypsin, and detergents. Thus, the data strongly suggest that yeast glycerol-P and DHAP acyltransferase activities represent dual catalytic functions of a single membrane-bound enzyme. Furthermore, since no acyl-DHAP oxidoreductase activity could be detected in yeast membranes, the DHAP pathway for glycerolipid synthesis may not operate in yeast.
 ...
PMID:Glycerolipid biosynthesis in Saccharomyces cerevisiae: sn-glycerol-3-phosphate and dihydroxyacetone phosphate acyltransferase activities. 2 65

We have investigated the localization of palmitoyl-CoA (hexadecanoyl-CoA) synthetase (EC 6.2.1.3) and cerotoyl-CoA (hexacosanoyl-CoA) synthetase in peroxisomes isolated from rat liver. Palmitoyl-CoA and cerotoyl-CoA synthetases, like acyl-CoA: dihydroxyacetone phosphate acyltransferase (EC 2.3.1.42), are present in the peroxisomal membrane. Trypsin treatment of intact peroxisomes led to the disappearance of both palmitoyl-CoA and cerotoyl-CoA synthetase activities but had little, if any, effect on L-alpha-hydroxy-acid oxidase (EC 1.1.3.15), D-amino acid oxidase (EC 1.4.3.3) or acyl-CoA:dihydroxyacetone phosphate acyltransferase. The latter three enzymes were inactivated if the trypsin treatment was preceeded by disruption of the peroxisomes by sonication. These results show that the active site, or at least domains essential for the activity of cerotoyl-CoA synthetase, like that of palmitoyl-CoA synthetase, is located on the cytosolic face of the peroxisomal membrane.
 ...
PMID:Topography of very-long-chain-fatty-acid-activating activity in peroxisomes from rat liver. 182 48

Upon differential centrifugation of guinea pig intestine mucosal cells homogenate, fatty acyl-CoA:NADPH oxidoreductase (long chain alcohol forming) was found to be enriched in the light mitochondrial (L) fraction (sedimenting between 66,000 x g min and 500,000 x g min) which contained mainly mitochondria, lysosomes, and peroxisomes. Peroxisomes (marker enzymes: catalase and dihydroxyacetone phosphate acyltransferase) present in the L fraction were separated from other organelles in a Nycodenz density gradient centrifugation employing a vertical rotor. By comparing the distribution of acyl-CoA reductase with different marker enzymes in the gradient, it was concluded that this reductase is primarily localized in the microperoxisomes (microbodies). The topography of the membrane-bound enzyme in the isolated organelles was studied by checking its lability toward trypsin in the absence and presence of the detergent Triton X-100. The results suggested that acyl-CoA reductase is localized on the outer surface (cytosolic side) of microperoxisomal membrane.
 ...
PMID:Peroxisomal localization of acyl-coenzyme A reductase (long chain alcohol forming) in guinea pig intestine mucosal cells. 206 6

The activities, properties, and steady-state kinetics of the five enzymes catalyzing the synthesis of 1-acyl- and 1-alkyl-sn-glycerol 3-phosphate in the cultured skin fibroblasts from Zellweger syndrome patients and normal controls were studied in detail. Judging from their Km and Vmax values, glycerol phosphate acyltransferase (EC 2.3.1.15), acyl/alkyl dihydroxyacetone phosphate reductase (EC 1.1.1.101), and acyl coenzyme A reductase (long-chain alcohol forming), appear to be affected only slightly by the absence of peroxisomes characteristic of the Zellweger syndrome. Glycerophosphate acyltransferase also showed no differences in N-ethylmaleimide sensitivity nor in inhibition by dihydroxyacetone phosphate between these cell types. Dihydroxyacetone phosphate acyltransferase (EC 2.3.1.42) and alkyl dihydroxyacetone phosphate synthase (EC 2.5.1.26) have altered activity and kinetic constants in homogenates from Zellweger syndrome fibroblasts. Dihydroxyacetone phosphate acyltransferase has similar Km (DHAP) values in both control and Zellweger syndrome cells; however, the value for the Vmax in Zellweger syndrome cells is only 6% of that found in the controls. This is interpreted as indicating that this enzyme is not defective in this disease but is simply present at a depressed level. Also, this enzyme activity has a maximum rate at pH 7.0-7.5 in the mutant cells as opposed to pH 5.4 in the controls. Acylation of dihydroxyacetone phosphate by control cell homogenate was stimulated by N-ethylmaleimide at both pH 5.7 and 7.5 whereas this activity from Zellweger syndrome cells was slightly inhibited at pH 5.7 and strongly inhibited at pH 7.5. In the absence of detergent, dihydroxyacetone phosphate acyltransferase in the Zellweger syndrome cells was much more labile to trypsin than in the control cells. Alkyl dihydroxyacetone phosphate synthase had a slightly higher Km (33 vs 17 microM) for palmitoyl dihydroxyacetone phosphate and a lower Vmax (0.07 vs 0.24 mU/mg protein) in the Zellweger syndrome cells as compared to controls. Although this is a substantial decrease in activity, it probably contributes little to the decreased rate of ether lipid synthesis in these cells. The major problem in this respect is apparently the loss of dihydroxyacetone phosphate acyltransferase activity. All of these enzymes, in both control and Zellweger syndrome cell homogenates, are sedimentable by centrifugation at 100,000g. Also, with the exception of dihydroxyacetone phosphate acyltransferase they had similar patterns of inactivation by heat in both cell types.
 ...
PMID:Properties of the enzymes catalyzing the biosynthesis of lysophosphatidate and its ether analog in cultured fibroblasts from Zellweger syndrome patients and normal controls. 364 70

Rat liver microsomal dihydroxyacetone phosphate acyltransferase, in contrast to the glycerophosphate acyltransferase, was found to be active at low pH (5.5), stable towards heat (55 degrees C, 15 min) and trypsin (in the absence of detergents) and was not inhibited by high concentrations of N-ethyl maleimide. Dihydroxyacetone phosphate acyltransferase is only slightly and non-competitively inhibited by sn-glycerol-3-phosphate whereas glycerophosphate acyltransferase is strongly inhibited by dihydroxyacetone phosphate in a competitive manner. Kinetic analysis indicates that this competitive inhibition is not due to the competition of two common substrates for the same active center of one enzyme. These results demonstrate that microsomal glycerophosphate acyltransferase and dihydroxyacetone phosphate acyltransferase are two distinct and separate enzymes.
 ...
PMID:Does microsomal glycerophosphate acyltransferase also catalyze the acylation of dihydroxyacetone phosphate? 648 17

Alkyl-dihydroxyacetone phosphate synthase (E.C. 2.5.1.26), the key enzyme in ether phospholipid biosynthesis, was demonstrated to be present in Trypanosoma brucei. The distribution of alkyl-dihydroxyacetone phosphate synthase was found to be identical to that of dihydroxyacetone phosphate acyltransferase (E.C. 2.3.1.42), which has previously been shown to be exclusively associated with the glycosome fraction (Opperdoes, F.R. (1984) FEBS Lett. 169, 35-39). Studies with gradient purified glycosomes indicated that the formation of alkyl-dihydroxyacetone phosphate was completely dependent on the presence of acyl-dihydroxyacetone phosphate. The glycosomal alkyl-dihydroxyacetone phosphate synthase activity was characterized with respect to its pH optimum, Triton X-100 sensitivity and the dependency on the concentration of the substrates palmitoyl-dihydroxyacetone phosphate and hexadecanol. Using thin-layer chromatographic and alkaline hydrolysis procedures the reaction product was identified as alkyl-dihydroxyacetone phosphate. Alkyl-dihydroxyacetone phosphate synthase was resistant to proteolytic inactivation by trypsin in intact glycosomes but not in Triton X-100 disrupted glycosomes. It is concluded that T. brucei glycosomes contain the enzymes responsible for glycero-ether bond formation analogous to mammalian peroxisomes.
 ...
PMID:Alkyl dihydroxyacetone phosphate synthase in glycosomes of Trypanosoma brucei. 761 57