The angiotensin I converting enzyme activity (kininase II, EC 3.4.15.1) was measured fluorimetrically in cerebrospinal fluid (CACE) of 154 patients with neurological disorders and 27 controls. The concentrations of total protein, albumin, and immunoglobulins G and A were also determined. There was no correlation between CACE and sex or age, but a slight positive relation between CACE and total protein and an inverse correlation between CACE and albumin were observed. Compared to controls, significantly elevated CACE was found in acute untreated CNS sarcoidosis (P less than 0.0001), followed by viral encephalitis, CNS syphilis, Huntington's disease, and multiple sclerosis (P less than 0.001). In treated CNS sarcoidosis, only a minor increase of CACE was observed (P less than 0.05). The determination of CACE can be used for the diagnosis of neurological disorders.

A spectrofluorimetric method was adapted for determination of angiotensin-Iconverting enzyme (ACE) in untreated native cerebrospinal fluid (CSF). Benzyloxycarbonylphenylalanyl- histidyl-leucine was applied as enzyme substrate. The biochemical behavior of ACE of CSF (CACE) was studied. The pH optimum was found to be 8.0 using borax phosphate buffer. The determination of Km was 10.7 ± 3.3 (SD) μmol/1. ACE could be blocked by 8-hydroxyquinoline (100%) and phenanthroline (80%), but only slight inhibition was observed by teprotide (43%), EDTA (40%) and captopril (31%). The influence of various drugs on CACE was also tested. The different biochemical behavior of CACE compared to serum ACE suggested that an isoenzyme exists in CSF. CACE has been found to be elevated in neuroimmunological and inflammatory disorders of the nervous system compared to levels in healthy controls.

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