Primate placental alkaline phosphatase

Volume 135, number 1 FEBS LETTERS November 1981 PRIMATE PLACENTAL ALKALINE PHOSPHATASE George J. DOELLGAST, Shirley C. WEI, Martha KENNEDY, Harold STILLS + and Kurt L. BENIRSCHKE* Department of Biochemistry, +Department of Comparative Medicine, Bowman Gray School of Medicine, Winston-Salem, NC 27103 and *San Diego Zoo, La Jolla, CA, USA Received 5 October 1981 1. Introduction In [ 1 ] we examined placental alkaline phosphatases of the 3 ape species chimpanzee, gorilla and orangutan. The chimpanzee and orangutan placental phosphatases resembled the human isoenzyme, in that they were heat-stable, phenylalanine-sensitive and cross-reactive with antibody to human placental phosphatase. The gorilla placental extracts had almost 3 orders of mag- nitude lower enzyme activity than the human, chim- panzee and orangutan placental extracts and the gorilla enzyme did not resemble the human. These results complemented other reports [2-5 ] of the absence of the 'human' isoenzyme in lower primates and a number of other mammalian species. This suggested to us that the human placental iso- enzyme may have appeared relatively late in primate evolution, but the absence of a similar isoenzyme in gorillas was puzzling. Here, we extend our previous results on ape species and. examine the placental phosphatases of several other lower primates. 2. Methods Enzyme assay, isolation of the IgG fraction, and assay of immunochemical reactivity of the alkaline phosphatases were as in [6]. Briefly, the assay of immunochemical reactivity is performed by binding of enzyme-antibody complexes to formalin-fixed Staphlyococcus A ceils. 3. Results and discussion A summary of our characterization of the primate placental phosphatases is given in table 1. Both chim- panzee species and 2 out of 3 orangutans had a heat- stable placental alkaline phosphatase at levels within that found in the human population. Three gorilla placentae had 3 orders of magnitude less heat-stable enzyme than the average human placenta. The 3 orang- utan placentae had a range of heat-stable activity of 2 orders of magnitude, from within 1 SD of the mean human assay value to 2 orders of magnitude lower. Consistent with [2-5 ], the old world monkey spe- cies Sumatran Macaque, African green, Langur and Colobus had very low levels of heat-stable enzyme but had readily measurable levels of heat-labile enzyme In the spider monkeys, the levels of heat-stable enzyme varied over 4 orders of magnitude, from 1/10th the mean level in humans to levels comparable to those in old world monkeys. Heat-stable enzyme was also found the single squirrel monkey placenta tested. Two characteristics used to distinguish the human placental isoenzyme, in addition to heat stability, are its sensitivity to amino acid and peptide inhibitors, and its reactivity with specific antisera. We used the 2 inhibitors L-phenylalanine [7] and L-phenylalanylgly- cylglycine [8] and rabbit and rhesus monkey antisera to the human placental enzyme to compare the heat- stable enzymes from these sources. Fig.1 contains the inhibition data. All enzymes were sensitive to inhibition by L-phenylalanine, 50% inhibition being attained at 1 mM (human)-5 mM (orangutan). L-Phenylalanylglycylglycine was a much more selective inhibitor of the human and ape enzymes, in that 50% inhibition was attained at 0.1 mM for the human, chimpanzee (not shown) and" pygmy chimpanzee enzymes, 0.6 mM for the orang- utan enzyme, and 10 mM for the squirrel and spider monkey enzymes. In this respect, the enzyme from Published by Elsevier/North-Holland Biomedical Press 00145793/81/0000-0000/$02.75 © 1981 Federation of European Biochemical Societies 61