Arnold A. Swanson

Elemental analysis in normal and cataractous human lens tissue

Abstract A detailed study is described which involves the employment of neutron activation analysis for the concentration of Br, Cd, Cl, Co, Cu, Fe, Ir, K, La, Mg, Mn, Mo, Na, Sb, Se and Zn in combined lens capsule and epithelium, cortex and nucleus. This study represents the first attempt in evaluating 17 elements at their concentration levels in lens tissue fractions at different age levels. Normal human lenses ranged in age groups from 0 – 5, 10 – 20, 50 – 60, 70 – 85 years. For cataractous lenses, age groups 40 – 55, 60 – 75 and 80 years and over were studied. Essential elements were found to decrease with age, and cataractogenesis. Suspected elements of biological function gave variable results, whereas nonessential elements increased with age and in cataractogenesis.

Mammalian lens dipeptidyl aminopeptidase III

Abstract An intracellular exopeptidase identified as dipeptidyl aminopeptidase III (DAP III) was found to be abundant in the bovine lens. The enzyme contained in aqueous extracts exhibited a marked preference, compared to other dipeptidyl-β-naphthylamides, for the release of Arg-Arg from Arg-Arg-2-NNap at the optimum pH 9.0 and 37°. The K m for this substrate was estimated to be 2.83 × 10 −5 M. Lens DAP III was inhibited by EDTA, p-chloromercuriphenyl sulfonate, and puromycin. Lens aminopeptidase activities measured at pH 7.5 on the β-naphthylamides of leucine, alanine, and arginine, included for comparison, suggested that not only is leucine aminopeptidase abundant, but also other aminopeptidases that appear to include alanine aminopeptidase and aminopeptidase B.

Proteases in human lenses and their possible significance

Proteases identified as exopeptidases including dipeptidyl II and III, phenylalanine, leucine, methionine, lysine and alanine aminopeptidases, and prolyl endopeptidase were found in extracts of human fetal lenses. Previous data from normal adult lenses were included for comparison. Except for prolyl endopeptidase and dipeptidyl peptidase II, all protease activities were lower in fetal lenses.

Dipeptidyl peptidase III of human cataractous lenses. Partial purification.

A partial purification of dipeptidyl peptidase III has been achieved from human cataractous lens. The specific activity was increased 45.5-fold over that of the original aqueous extract. The exopeptidase exhibited a marked preference for the release of Arg-Arg from Arg-Arg-2-NNap at the optimum pH 8.8 and 37 degrees. The Km for this substrate was estimated to be 6.061 X 10(-3). Lens DPP III was inhibited by EDTA, p-chloromercuriphenyl sulfonate, puromycin and DFP. The preparation contained leucyl aminopeptidase and a neutral endopeptidase as contaminating proteases.

Isolation and Purification of Arylamidase from Human Lenses

A procedure is described for the resolution of arylamidase from human lenses. Purified arylamidase will hydrolyze leucyl-, arginyl- and lysyl-β-naphtylamides. It has been shown to be ependent on metal ions for activity. Human arylamidase required dithiothreitol for stability; activity was increased by β-mercapto-ethanol and cysteine and inhibited by p-chloromercuribenzoate. The properties of human lens arylamidase is distinct from leucine aminopeptidase (EC 3.4.1.1) or esterases.

Studies on Proteolytic Activity in Bovine Lenses with Ageing

A longitudinal study of two endopeptidases including a neutral protease and a proteinase (catheptic activity) in bovine lenses was evaluated. The neutral protease shows an increase in activity during

The identification of prolyl endopeptidase in bovine lenses: a preliminary report

A new neutral endopeptidase having the properties of prolyl endopeptidase was detected in bovine lenses. The enzyme hydrolyzed the prolyl bond in the newly-developed fluorogenic substrate, t-butyloxycarbonyl-Arg-Pro-2-NNap, optimally at pH 8 and 37 degrees. The Km value was estimated to be 0.033 mM. An approximately 4-fold purification was achieved. DFP completely inhibited the hydrolysis of Boc-Arg-Pro-2-NNap by the endopeptidase.

Investigation of Proteolytic Activity in Bovine Lenses with Age I. the Exopeptidases

Bovine lens exopeptidases including an esterase, leucine aminopeptidase and a triglycinpeptidase were assayed in lenses ranging in age from a few days old to eighteen years of age. Esterase activity increased in lenses in excess of 15 years. Leucine aminopeptidase showed significant increase during the early postnatal growth phase and again after 15 years of age. Triglycinpeptidase gave similar activities, however, on a much lower level of magnitude.