IMMUNOLOGICAL EVIDENCE FOR 3 ISOFORMS OF AMP DEAMINASE (AMPD) IN MATURE SKELETAL-MUSCLE

Four rabbit polyclonal antisera to purified AMP deaminase (AMPD) isozy mes were used to precipitate homogenate AMPD activity from dissected g racilis, soleus and gastrocnemius muscles of the cat, rabbit, rat, mou se, Rhesus monkey, human and toad. The antisera were also tested again st other unusual muscles: autonomically innervated striated muscle of the upper esophagus (UEM), skeletal muscle of patients with myo-AMPD d eficiency and extraocular muscles (EOM) of humans and Rhesus monkeys. The reference antiserum, M, prepared against human psoas muscle AMPD, precipitated > 90% AMPD from all primate skeletal muscles tested, and from type-2 muscles of all mammals tested, but < 75% from cat and rode nt soleus, toad gastrocnemius and primate UEM, EOM and myo-AMPD defici ent muscles. Thus, a second isozyme was clearly indicated. Antibody B, against rat liver and kidney AMPD, had no effect with any muscle spec imen. Antibody C, against rat heart AMPD, produced additive precipitat ion of AMPD from soleus of rat and mouse, while antibody El, against h uman red cell (and heart) AMPD, produced additive AMPD precipitation f rom toad gastrocnemius, cat soleus and muscles of several AMPD-deficie nt humans. A second AMPD isozyme thus accounted for as much as 25% of total activity in some animal red muscles, but no more than 5% in huma n mixed muscles. At least one more isozyme is needed to account for mu scle AMPD unreactive with all antibodies tested in rabbit soleus, toad gastrocnemius and primate UEM and EOM. A list is appended of the appr oximate AMPD activity in various human cells and tissues.