Knoop, Franz

Another important piece of the puzzle came from the work of Carl Martius and Franz Knoop, who showed that citric acid could be converted to isocitrate and then to a-ketoglutarate. This finding was significant because it was already known that a-ketoglutarate could be enzymatically oxidized to succinate. At this juncture, the pathway from citrate to oxaloacetate seemed to be as shown in Figure 20.3. Whereas the pathway made sense, the catalytic effect of succinate and the other dicarboxylic acids from Szent-Gyorgyi s studies remained a puzzle. 

The earliest clue to the secret of fatty acid oxidation and breakdown came in the early 1900s, when Franz Knoop carried out experiments in which he fed dogs fatty acids in which the terminal methyl group had been replaced with a... 

FIGURE 24.5 The oxidative breakdown of phenyl fatty acids observed by Franz Knoop. 

Mohs scale after Franz, 1850 1 after Pfaff, 1884 after Poschl, 1909 m ON -14 O CO u 3 C3 after Hodge and McKay, 1934 after Auerbach, 1936 i after Knoop et al., 1939 Corundum after Winchell, 1945 after Khrushchev, 1947 j after Taylor, 1949 after Dinritreva, 1949... 

In 1904, Franz Knoop made a critical contribution to the elucidation of the mechanism of fatty acid oxidation and demonstrated that most of the fatty acids are degraded by oxidation at the p-carbon. p-Oxidation of fatty acids takes place in mitochondria. Fatty acids are activated before they enter into mitochondria for oxidation. 

In 1904, Franz Knoop outlined a scheme for the biological oxidation of fatty acids that was shown—50 years later—to be correct. In his key experiments, he fed rabbits fatty acids of formula C5H5(CH2)nCOOH. When the side chain (/f + 1) contained an even number of carbons, a derivative of phenylacetic acid, C6H5CH2COOH, was excreted in the urine an odd number, and a derivative of benzoic acid was excreted. What general hypothesis can you formulate from these results ... 

The year 23004 marked the centenary of two important discoveries in the field of metabolism The discovery of beta-oxidation of fatty acids by Franz Knoop (1904), and the discovery of the oxygen dependence for normal pump function of the heart by Hans Winterstein (1904).2 The year 2004 also marked the 50th anniversary of the discovery, by Richard Bing and his colleagues, that the human heart prefers fatty acids for respiration.3... 

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