Glycolytic Enzymes in Polyamine-Treated Bovine Retina

I. Venza, A. Valenti, P. Ruggeri¹, L. Denaro¹, D. Teti

Received May 24, 1999
Accepted October 27, 1999

Summary
The retina is characterized by glycolysis under aerobic conditions, mediated by lactate dehydrogenase isoenzyme-5 (LDH-5) as well as by the soluble isoenzyme of malate dehydrogenase. Bovine retina LDH and MDH isoenzymes and their activities were studied after polyamine treatment. Our results showed that LDH-5 isoenzyme presented the highest activity in untreated as well as in putrescine-treated retina. Decreased activity was present when the retina was treated with spermidine or spermine. It was demonstrated that retinic LDH-5 had a high affinity for lactate which enabled the isoenzyme to be more effective than the other LDH isoenzymes in the conversion of NADH to NAD. Therefore, the putrescine enhancing LDH-5 activity appeared to be capable of stimulating NAD-mediated rhodopsin regeneration. Putrescine induced a marked increase of both MDH isoenzymes – soluble (s-MDH) and mitochondrial (m-MDH), while spermine and spermidine mostly affected the soluble form of the enzyme. Putrescine induced a three-fold increase in
s-MDH and m-MDH activities, while spermine and spermidine induced a four to five-fold increase in s-MDH. These results document the differential effects of polyamine treatment on LDH and MDH isoenzyme activities.

Key words
LDH isoenzymes · MDH isoenzymes · Polyamines · Retina

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Prof. Diana Teti, M.D., University of Messina, Faculty of Medicine and Surgery, Institute of General Pathology, Messina, Italy. Fax: +39-90-2213341. e-mail: dteti@unime.it