Placenta, amine oxidases

Human vascular adhesion protein (HVAP) is involved in targeting lymphocytes to inflamed tissue following infection (Salmi and Jalkanen, 1997). Interestingly, the sequence of HVAP cDNA is identical to that reported for the amine oxidase from human placenta (Smith et al., 1998), and HVAP has been shown to have amine oxidase activity. The partial three dimensional structure of HVAP has been modelled based on homology to the known 3-D structure of ECAO (Salminen et at., 1998). There is an equally intriguing sequence identity between mouse vascular adhesion protein and the membrane-bound amine oxidase associated with adipoeytes (Bono et at., 1998). 

Diamine oxidase occurs, like amine oxidase, in bacteria, animals, and plants [133]. The comparison of amino acid sequences of the amiloride-binding protein from human kidney, rat colon, diamine oxidase from human placenta, pig kidney, and amine oxidase from Hansenula polymorpha and lentil seeds has shown that the amiloride-binding protein and diamine oxidase are identical proteins[29]. The amiloride-binding protein was previously postulated to function as an epithelial sodium-transporter. While its physiological function is still... 

Recently, the cofactor peptides have also been isolated from semicarbazide-sensitive amine oxidases purified from bovine and porcine aortas [52], sequenced and confirmed to contain the topa quinone. The same topa quinone consensus sequence was also found in the primary structures of amine oxidases from human kidney [53], human retina [54] and rat colon [55], so called amiloride-binding proteins , and amine oxidase from human placenta [56] that shows 81% identity with bovine plasma amine oxidase [57], bovine lung amine oxidase [58], and amine oxidases from pea and lentil seedlings [59,60], chick pea seedlings [61], and Arabidopsis thaliana [62] obtained by the molecular cloning of respective DNAs. 

Diamine Oxidases. Diamine oxidases are enzymes that also oxidize amines to aldehydes. The preferred substates are aliphatic diamines in which the chain length is four (putrescine) or five (cadaverine) carbon atoms. Diamines with carbon chains longer than nine will not serve as substrates but can be oxidized by monoamine oxidases. Secondary and tertiary amines are not metabolized. Diamine oxidases are typically soluble pyridoxal phosphate-containing proteins that also contain copper. They have been found in a number of tissues, including liver, intestine, kidney, and placenta. 

Monoamine Oxidases (MAO) There are two MAO isoforms, MAO A and MAO B, both of which are flavoen-zymes that oxidize a wide array of neurotransmitter amines. However, they can also biotransform some xenobiotics. Both MAO isoforms consist of approximately 520 amino acid residues and share approximately 70% sequence identity. Their molecular weights are about 58K Daltons. Both isoforms are expressed in most tissues, though not necessarily in equivalent amounts. More MAO is found in liver and placenta, and least in the spleen. Actually MAO-B is... 

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