Proteases in the Emory mouse cataract.

Exopeptidases identified as dipeptidyl peptidase III and leucine aminopeptidase, and an endopeptidase, prolyl endopeptidase, were found in the Emory Mouse cataract and the Cataract Resistant mouse lens extracts. The specific activity measured on Arg-Arg-2-NNap for DPP III and the hydrolysis of Boc-Arg-Pro-2-NNap for prolyl endopeptidase were higher in the Emory Mouse cataractous lens extract. A relatively high rate of hydrolysis of the beta-naphthylamide of leucine aminopeptidase was present in both mouse categories; however, the Cataract Resistant mouse lens had approximately double the protease activity of the Emory Mouse cataract.

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.

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.

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.

Age-related changes in the proteolytic enzymes of mammalian lens.

A longitudinal study has been conducted on three exopeptidases which include an esterase, leucine aminopeptidase, and a triglycinopeptidase and two endopeptidases, a neutral protease and a proteinase or catheptic activity in bovine lenses. The esterase and leucine aminopeptidase behave similarily showing increased activities with aging. Triglycinopeptidase has a somewhat lower order of magnitude when compared to the other exopeptidases. The neutral protease shows initially high activity early in the developmental life period, whereas, the proteinase or catheptic activity indicates a continuous increase with aging. Data whereas, the proteinase or catheptic activity indicates a continuous increase with aging. Data is also provided on enzymic activity in the different sections of the lens which include the combined anterior cortex and epithelium, lens nucleus, posterior cortex, and equatorial ring.

Human placental cathepsin B1. Isolation and some physical properties.

A reproducible procedure for the isolation, from human placenta, of a cathepsin B1 in a homogeneous state, demonstrated by electrophoretic, ultracentrifugal and enzymic criteria, was carried out. The pH optimum was near pH5.5. The placental enzyme catalysed the release of acid-soluble u.v.-dense products from haemoglobin and myoglobin. It was inhibited by heavy metals and several compounds which react with the thiol groups. The optimum temperature was between 37 degrees and 42 degrees C. The molecular weight of the enzyme was calculated to be 24250.

Human senile cataractous lens protease. Isolation and some chemical characteristics.

A proteolytic enzyme was isolated from human senile cataractous lens by anion-exchange and gel-filtration chromatography. Sedimentation and zone-electrophoretic experiments indicated a high degree of homogeneity for the enzyme. A molecular weight of 27000 was calculated from measurements of sedimentation velocity and diffusion coefficient. Chelating agents decreased activity which could be restored by addition of certain bivalent metal ions. Di-isopropyl phosphorofluoridate and phenylmethanesulphonyl fluoride inhibit the proteolytic activities. Optimum rates of hydrolysis were observed at pH5.2.