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Deoxynucleotide sequencing of a cDNA for the dihydrolipoamide acetyltransferase (PDC‐E2) component of human pyruvate dehydrogenase complex (PDC) revealed an open reading frame of 1848 base pairs corresponding to a leader sequence of 54 amino acids and a mature protein of 561 amino acids (59 551 Da). Both an amino‐terminal lipoyl‐bearing domain and a carboxy‐terminal catalytic domain are present in the deduced amino acid sequence. The lipoyl‐bearing domain contains two repeating units of 127 amino acids, each harboring one lipoic acid‐binding lysine. Thus, mammalian PDC‐E2 differs as to the number of lipoic acid‐binding sites from other dihydrolipoamide acyltransferases in both prokaryotic and eukaryotic organisms.

The molecular basis of dihydrolipoamide dehydrogenase (E3; dihydrolipoamide:NAD+ oxidoreductase, EC 1.8

In this paper, we report the overexpression and single-step purification of recombinant wild-type and site-directed mutants of human dihydrolipoamide dehydrogenase in Escherichia coli and detailed spectroscopic studies aimed at understanding the catalytic mechanism of this enzyme. One mutation (K37E) has been identified in a patient lacking dihydrolipoamide dehydrogenase activity and has been reported previously (Liu, T.-C., Kim, H., Arizmendi, C., Kitano, A., and Patel, M. S. (1993) Proc. Natl. Acad. Sci. USA. 90, 5186-5190), while the other two mutations were previously generated specifically to address the role of the active-site base (His-452) and its ion pair (Glu-457). Circular dichroic and fluorescence spectroscopic data illustrate the role of these amino acids in maintaining the structure and function of human dihydrolipoamide dehydrogenase. While mutant H452Q is severely crippled in catalysis of the physiological reaction, the reverse reaction is affected in the E457Q mutant. The K37E mutant shows very little deviation from the wild-type enzyme.

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D-methionine is a sulfur-containing amino acid that can act as a potent antioxidant. Anorexia and nephrotoxicity are side effects of cisplatin. The protective effects of D-methionine on cisplatin-induced anorexia and renal injury were investigated. The model of chronic cisplatin administration (5 mg/kg body weight) involved intraperitoneal injection on days 1, 8, and 15 and oral D-methionine (300 mg/kg body weight) coadministration daily for 20 days. On the 21st day of treatment, food intake and body weight in the cisplatin-treated group significantly decreased by 52% and 31%, respectively, when compared with a control group. D-methionine coadministration with cisplatin decreased food intake and body weight by 29% and 8%, respectively. In cisplatin-treated rats, white blood cell, mean corpuscular volume, and platelet values significantly decreased, while mean corpuscular hemoglobin concentration significantly increased by 8.6% when compared with control rats. Cisplatin administration resulted in significantly decreased feeding efficiency, elevated renal oxidative stress, and reduced antioxidative activity. Leukocyte infiltration, tubule vacuolization, tubular expansion, and swelling were observed in the kidneys of cisplatin-treated rats. Oral D-methionine exhibited an antianorexic effect, with improvement in food intake, feeding efficiency, and hematological toxicities, as well as a protective effect against nephrotoxicity by elevated antioxidative activity. D-methionine may serve as a chemoprotectant in patients receiving cisplatin as part of a chemotherapy regimen.

A cDNA clone (1423 base pairs) comprising the entire coding region of the precursor form of the a subunit of pyruvate dehydrogenase (Ela)