Properties of the branched-chain 2-hydroxy acid/2-oxo acid shuttle in mouse spermatozoa.
Operation of the branched-chain 2-hydroxy acid/2-oxo acid shuttle for the transfer of reducing equivalents in mitochondria of mouse spermatozoa was studied in vitro in reconstituted systems. Results show that the branched-chain 2-oxo acids within the mitochondria are offered several metabolic pathways. (a) Decarboxylation: mouse sperm mitochondria possess high branched-chain 2-oxo acid decarboxylase activity. (b) Recycling to the cytosol by using a transport system which can be inhibited by alpha-cyano-3-hydroxycinnamate and pH 6.8. (c) Transamination to the corresponding amino acids: experiments presented indicate that leucine formed from 4-methyl-2-oxopentanoate may pass to the external phase, re-initiating the cycle. These two last possibilities would allow autocatalytic operation of the shuttle. The branched-chain 2-hydroxy acids apparently do not utilize the monocarboxylate carrier to penetrate the mitochondria.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D005971:Glutamates / Q000494:pharmacology; D018698:Glutamic Acid; D006880:Hydroxy Acids / Q000378:metabolism*; D066298:In Vitro Techniques; D007651:Keto Acids / Q000378:metabolism*; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D007930:Leucine / Q000378:metabolism; D008297:Male; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D011767:Pyruvate Decarboxylase / Q000378:metabolism; D011773:Pyruvates / Q000378:metabolism; D019289:Pyruvic Acid; D013094:Spermatozoa / Q000187:drug effects / Q000378:metabolism*; D014018:Tissue Distribution
D005971:Glutamates; D006880:Hydroxy Acids; D007651:Keto Acids; D007773:Lactates; D011773:Pyruvates; D019344:Lactic Acid; D018698:Glutamic Acid; D019289:Pyruvic Acid; D011767:Pyruvate Decarboxylase; D007930:Leucine