Proteolytic Enzymes in Human Leukemic Lymphoid Cells. III. Aminopeptidases, Angiotensin-Converting Enzyme, and Its Inhibitor in Cells of Different Immunological Phenotype

L. A. Lokshina^1*, T. A. Gureeva¹, Yu. E. Elisseeva¹, N. V. Golubeva¹, E. V. Kugaevskaya¹, O. N. Lubkova¹, and R. S. Samojlova²

¹Institute of Biomedical Chemistry, Russian Academy of Medical Sciences, Pogodinskaya ul. 10, Moscow, 119832 Russia; fax: (095) 245-0857

²Hematology Research Center, Russian Academy of Medical Sciences, Novozykovskii pr. 4a, Moscow, 125167 Russia; fax: (095) 212-4252

^* To whom correspondence should be addressed.

Received July 3, 1998

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Activities of plasma membrane proteinases such as angiotensin-converting enzyme (ACE), aminopeptidases, and dipeptidyl peptidase IV (DPP-IV) were determined in lymphoid cells of various immunological phenotype which were obtained from 30 patients with lymphoproliferative diseases. The enzyme activities significantly varied depending on the immunological phenotype and stage of cell differentiation, but no correlation was found between activities of ACE, DPP-IV, and aminopeptidases in the cells of different type. The cell lysates studied contained at least two classes of aminopeptidases: metal- and sulfhydryl-dependent enzymes. A sulfhydryl-dependent aminopeptidase with activity optimum at pH 8.5-9.0 was found for the first time and is suggested to be from a poorly studied aminopeptidase family. In addition to ACE, lysates of leukemic T- and B-cells were found to contain an inhibitor of ACE which was not previously described for these cells.

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KEY WORDS: angiotensin-converting enzyme, aminopeptidases, dipeptidyl peptidase IV, plasma membrane proteinases, inhibitor of angiotensin-converting enzyme, leukemic lymphoid B- and T-cells, antigens, differentiation

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