Malate synthetase

With the stereochemistry of the citrate lyase reaction determined, that of the Si citrate synthetase (the common enzyme) was established as shown in Fig. 70. Condensation of (J )-acetic-d, t acid (configuration known by synthesis) with oxalo-acetate gives what turns out to be mainly (2S,3/ )-citric-2-d,2-/ acid (112).41 When this acid is then cleaved with citrate lyase, the major product is (/ )-acetic-d, t acid, as established by the malate synthetase/fumarase diagnosis. It follows that both the Si-citrate synthetase and citrate lyase reactions must involve the same stereochemical course. Since that of the lyase reaction is inversion (vide supra), that of the Si synthetase reaction must be inversion also. And since the overall stereochemical result shown in Fig. 70 is not dependent on the magnitude of the... 

The actual example 158) related to fatty acid biosynthesis the case of malate synthetase here discussed is hypothetical. 

Citrate Synthetase Isocitrate Lyase Malate Synthetase Malate Dehydro- genase Succinate Dehydro- genase Fumarase... 

Following are a set of assay conditions for marker enzymes of mitochondria (citrate synthetase, malic dehydrogenase, fumarase, and succinate dehydrogenase) and glyoxysomes (citrate synthetase, malate synthetase, and malic dehydrogenase). Some or all of these activities may be assayed across the density gradient. Their quantitative distribution is shown in Table 9-2. 

Malate Synthetase. Assay is by a modification of the procedures of Hock and Beevers. The assay mixture contains, in a final volume of... 

Yamamoto, Y. Malate synthetase in higher plants Plant Physiol. 35 (1960) 102-108. 

Malate synthetase B, R Martinez-DeDrets and Arias (1972) Lawrie and Wheeler (1975) Kurz and LaRue (1977) Mulongoy and Elkan (1977) Sutton and Mahoney (1977) Johnson et al. (1966) Kurz and... 

Fig. 2. (A) The glyoxylate cycle as a bypass of the TCA cycle (after Komberg and Krebs, 1957). (B) The glyoxylate cycle as it functions in the glyoxysome, showing the production of succinate from 2 mol of acetyl-CoA. The five steps constituting the cycle are catalyzed by the following enzymes (1) citrate synthetase, (2) aconitase, (3) isocitrate lyase, (4) malate synthetase, (5) malate dehydrogenase.

From the fact that the glyoxylate and TCA cycles have several enzymes (citrate synthetase, aconitase, malate dehydrogenase) in common it appeared axiomatic that they must operate together in the same intracellular compartment, the mitochondrion. Early experiments with crude particulate pellets containing mitochondria gave only partial support to this view since, although malate synthetase was present in such preparations, most of the isocitrate lyase was present in the supernatant fraction (Yamamoto and Beevers, 1961 Marcus and Velasco, 1960). 

Enzymes (1) Lipases (2) Fatty acid thiokinase (3) Acyl CoA dehydrogenase (4) Crotonase (5) jS-Hydroxyacyl CoA (6) )5-Ketoacyl thiolase (7) Citrate synthetase (8) Aconitase (9) Isocitrate lyase (10) Malate synthetase (11) Malate dehydrogenase (12) Catalase (13) Succinate dehydrogenase (14) Fumarase (15) Malate... 

Fig. 6.12A and B. Variation in glyoxysomal isocitrate lyase ( ) and malate synthetase (o) in (A) isolated peanut cotyledons incubated in darkness and (B) of these enzymes plus catalase ( ) in the glyoxysomal fraction from the scutellum of germinated maize Zea mays). After Longo and Longo, 1970 [85]... 

Fig. 6.13. (A) Diagrammatic representation of the appearance of cucumber seedlings grown under a 12-12 h light-dark cycle. (B) Changes in glyoxysomal and peroxisomal enzyme activities in homogenates of cucumber cotyledons grown as in (A). Enzyme activity glyco-late oxidase ( ), nmol substrate consumed/min/cotyledon isocitrate lyase ( ), 0.1 x nmol substrate consumed/min/cotyledon malate synthetase (a), 0.04 x nmol substrate consumed/ min/cotyledon and catalase (x), 0.2 x units/cotyledon. After Trelease etal., 1971 [139]...

Isocitrate lyase and malate synthetase activity Stimulated ... 

However, by an extraordinary coincidence, a paper (to which our attention was drawn by Professor Krebs) appeared at just this time in the Journal of the American Chemical Society which brought the possible metabolism of glyoxylate very sharply to our notice. D. T. O. Wong and S. J. Ajl reported that extracts of E. coli could promote the condensation of acetyl coenzyme A and glyoxylate to form malate this reaction was, of course, formally analogous to that whereby citrate was formed from acetyl coenzyme A and oxaloacetate. The authors termed the novel enzyme malate synthetase . The blunderbuss experiment we had done suggested that this enzyme was present also in the Pseudomonas... 

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